Integrated Life Cycle Design of Structures

Integrated Life Cycle Design of Structures

Current objectives towards sustainable building and civil engineering are leading to new challenges for the construction industry. The life cycle engineering approach takes into account all aspects of construction practice, from design, construction, and service life management, to demolition and the recycling of materials. Traditionally the process of design has concentrated on the construction phase itself, with the primary object being to optimise efficiency and minimise costs during development and construction. With the move towards more sustainable development comes the need for this short-term approach to be expanded to encompass the entire service life of the structure. This book explains how to optimise structures for their entire design life, through an optimum integrated life cycle design process. Sustainability and performance issues are detailed. Integrated Life Cycle Design of Structures provides a comprehensive account of this rapidly emerging field. It is essential reading for civil and structural engineers, designers, architects, contractors, and clients. Asko Sarja is Research Professor of Building Technology in Structural Engineering, Technical Research Centre of Finland (VTT).

Integrated Life Cycle Design of Structures Asko Sarja

London and New York

First published 2002 by Spon Press 11 New Fetter Lane, London EC4P 4EE Simultaneously published in the USA and Canada by Spon Press 29 West 35th Street, New York, NY 10001 Spon Press is an imprint of the Taylor & Francis Group This edition published in the Taylor & Francis e-Library, 2005. “To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.” © 2002 Asko Sarja All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging in Publication Data Sarja, Asko. Integrated life cycle design of structures/Asko Sarja. p. cm. Includes bibliographical references and index. 1. Buildings, 2. Structural engineering. 3. Product life cycle. 4. Building materials—Service life. 5. Sustainable development. I. Title. TH845 .S35 2002 624.1–dc21 2001049380 ISBN 0-203-30234-6 Master e-book ISBN

ISBN 0-203-34614-9 (Adobe eReader Format) ISBN 0-415-25235-0 (Print Edition)

Contents

List of tables

v

List of figures

vi

Preface

viii

Introduction

x

1

Framework of integrated structural life cycle design

1

2

Design process

9

3

Life cycle design methods

24

4

Design for recycling using concrete and masonry as an example CHRISTOPH MÜLLER

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5

Integrated life cycle design of materials TOSHIO FUKUSHIMA

88

6

Conclusions and needs for further development

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Appendix 1:

List of international and national regulations, codes and standards

112

Appendix 2:

Guidebooks, certification and manuals

118

Glossary

124

Index

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Tables

1.1 2.1 2.2 2.3

Thermal parameters defining levels of energy efficiency in buildings 7 Integrated life cycle design process and central methods for application 10 Design phases, tasks and methods of integrated life cycle design 11 Specification of performance properties for alternative structural solutions at a module level using 14 a multi-storey apartment building as an example 3.1 Design methods for different types of requirements of use 25 3.2 Integrated life cycle design process and central methods for application in civil engineering 26 3.3 Specification of performance properties for the alternative structural solutions on a module level; 30 as an example a bridge 3.4 Estimation of the recycling efficiency coefficient kr 34 3.5 General attributes and sub-attributes of structures 46 3.6 An example decision-making table 51 3.7 Methods used in aggregating life cycle quality (LCQ) parameters from technical life cycle 53 parameters 3.8 A model of the modularised service life planning scheme of a building with a design life of 50 56 years 3.9 Residual value method and multiplication coefficient method in the optimisation of target service 57 life of building modules 3.10 The analogy between static limit state design and durability limit state design with the lifetime 61 safety factor method 3.11 Safety classification of durability design and the corresponding safety factors 66 4.1 Construction planning and building stages and their influence on the avoidance and reuse of 76 wastes 4.2 Classification of recycled coarse aggregates for concrete 78 4.3 Provisions for the use of concrete with recycled aggregates 79 4.4 Factors in the evaluation of the material properties of concrete with recycled aggregates 80 5.1 Experimental results of recycled concrete mixed with pulverised FRP powder (curing time 28 102 days) 5.2 Experimental results of fluidised concrete mixed with pulverised FRP powder (curing time 7 104 days) 5.3 Material properties and test methods for thermoplastic FRPs 102

Figures

0.1 Main aspects of life cycle quality 1.1 Framework of integrated building design 1.2 Modules of the integrated life cycle design 2.1 Multiple-attribute decision-making procedure 2.2 Flow chart of the durability design procedure, concrete structures as an example 2.3 The increase of failure probability: illustrative presentation 3.1 Classification of design methods of integrated life cycle design 3.2 Overview of the hierarchical modular building product system 3.3 An environmental life cycle costing scheme 3.4 Procedural schema from functional requirements to technical specifications 3.5 A ‘house of quality’ 3.6a Demands and their priorities 3.6b Functional attributes and their priorities 3.7a Design objectives for a housing project, phase 1 3.7b Design objectives for a housing project, phase 2 3.8 Design priorities for a nursery school 3.9 Analysis of two design solutions and comparison to properties of a typical nursery school building 3.10 Hierarchy of the structural system of buildings 3.11 Aggregation scheme for LCQ parameters 3.12 The increase of failure probability 3.13 Relationship between mean service life and target service life 3.14 The meaning of lifetime safety factor in a performance problem 3.15 Determination of lifetime safety factors with normally distributed D 3.16 Flow chart of the durability design procedure 4.1 Connected materials cycles based on the example of cement-and lime-based building materials 4.2 Examples for walls with a coefficient of heat transfer k 0.44 W/(m2K) 4.3 Classification of the separability and the recycling capability of the walls shown in Figure 4.2 5.1 Triangluar relationship between building materials, the global environment and the dwelling environment 5.2 Triangular relationship between resource problems, deterioration problems and environmental problems 5.3 Life, maintenance and recycling of buildings 5.4 Service life and its prolongation of buildings and reuse of demolished components 5.5 Fundamental concepts for environmentally-concious materials design (eco-materials design for composite structural building materials and components)

xii 4 5 17 19 20 25 28 32 39 40 41 41 43 43 45 45 48 54 60 62 63 64 66 77 83 84 89 90 91 92 93

vii

5.6 Environmentally-conscious materials design (eco-material design) of pre-cast lightweight contcrete with continuous fibre reinforced plastic (FRP) reinforcement 5.7 Selection and evaluation system for FRPRC for effective use in construction 5.8 Repeated partial (cascade) recycling of lightweight precast concrete 5.9 Comparison of new reinforced concrete with FRP reinforcement with traditional reinforced concrete with steel reinforcement 5.10 New external thermal insulation systems taking recyclability and long service life into consideration 5.11 Life cycle design aimed at compatibility of long building service life with environmental harmony (eco-balance performance) 5.12 Procedures for environmentally-conscious life cycle design for composite structural building materials and components 5.13 Prediction of changes in atmospheric CO2 in the twenty-first century 5.14 Evaluation indicators for repeated partial recycling of FRPRC 5.15 Relationship of city area and waste occupancy area 5.16 Comparison of predicted service life between new reinforced concrete with FRPRC reinforcement and ordinary reinforced concrete with steel reinforcement 5.17 Setting the physical service life of reinforced concrete components by taking account of the suppressive effects of surface finishing materials 5.18 Method of accelerated carbonation testing by step-response modelling the tendency to increase the concentration of atmoshperic CO2 5.19 Progress of neutralisation of various types of concrete by step-response method

94 95 96 97 98 98 99 99 100 100 102 103 106 108

Photograph 5.1 Outline of newly developed recyclable continuous fibre reinforced thermoplastics

107

Preface

Our society is living through a period of great change, in which we can also see changes in the central goals and requirements of construction techniques. The challenge to the present generation is to lead rapid development of a global economy towards sustainability in relation to our entire society, economy, social welfare and ecology. Buildings, and civil and industrial infrastructures are the longest lasting and most important products of our society. The economic value contained in buildings, and civil and industrial infrastructures are, to say the least, significant; and the safe, reliable and sound economic and ecological operation of these structures is greatly needed. In industrialised countries buildings and civil infrastructures represent about 80 per cent of national property. Construction plays a major role in the use of natural resources and in the development of the quality of the natural environment in our time. Consequently, building and civil engineering can make a major contribution to the sustainable development of society. The sustainability of buildings and built environment can, in short, be defined as thinking in time spans of several generations. Sustainability includes social aspects (welfare, health, safety, comfort), economic aspects, functional aspects (usability for changing needs), technical aspects (serviceability, durability, reliability) and ecological aspects (consumption of natural resources such as energy, raw materials and water; air, water and soil pollution, waste production; and impact on biodiversity), all treated over the entire life cycle of the built facilities. It could be claimed that a built facility can only be as good as its design. I have proposed a technical definition for sustainable building as: ‘Sustainable building is a technology and practice which meets the multiple requirements of the people and society in an optimal way during the life cycle of the built facility’ (Sarja, 1997). Design is an important part of construction: translating the requirements of owners, users and society into performance requirements of the structural system; creating and optimising structural solutions which fulfil those requirements and finally, proving through analysis and dimensioning calculations, that these requirements are fulfilled. The new model of integrated life cycle design presented in this book includes a framework for integrated structural life cycle design, a description of the design process and its phases, special life cycle design methods regarding different aspects like life cycle costs, life cycle environmental impact, design for reuse and recycling, service life design, durability design, multiple attribute optimisation and multiple attribute decision-making. This book provides methods and methodologies for design of structures in order to meet the requirements of sustainable developments during the entire service life of the structures. The scope of this book covers both the loadbearing and non-loadbearing structures of buildings, bridges, towers, dams and other structural facilities. This book includes:

ix

• • • •

definitions and terms; framework schedule of the integral structural design; systematics and central methods of the environmental structural design; and examples of applications.

Target groups and users of the book are expected to include: architects, structural engineers, civil engineers, clients of construction, contractors, suppliers of materials, components and modules and standards organisations. The methodology and the methods present here are well suited for the use in the development of new building concepts and new structural solutions and products. The origin for this kind of integrated life cycle design was the idea of the author who concluded that the sustainability aspects have to be quantified and calculation methods have to be developed (Sarja 1994, Sarja 1995). This concept was then realised in the work of the international working committee: RILEM TC 172 EDM/CIB TG22 ‘Environmental Design Methods in materials and structural engineering’, which was active in years 1996–2000 (Sarja 2000). The committee consisted of twenty-two members and corresponding members under the chairmanship of the author, with Mr. Julian Kümmel as the Secretary of the group. I expect the results of the commission’s work to be an active starting point towards the final formulation of life cycle design. Chapter 4 by Christoph Müller, Germany and Chapter 5 by Toshio Fukushima, Japan, originated from the commission’s report. After preparing the report of RILEM/CIB working group, the results were published in an article in the RILEM journal Materials and Structures in 1999 (Sarja 1999). I have used the working group report as a core of this book, but have developed it further and added a considerable amount of new material from results of my other work and from other sources, and have totally reorganised the content into its current form. Integrated life cycle design is still at a phase of rapid development, and this is the start of the final formulation of a new integrated design process and methodology, which in future will serve as a general design culture. The next step on this path will be an integration of the design, management and maintenance planning of buildings and civil infrastructures into a comprehensive life time engineering. The practical implementation can be carried out through international and national standards, guidelines and computer tools. Asko Sarja Espoo, Finland, June 2001 References Sarja, A. (1994) ‘Development towards the ecological and recyclable building materials technology’. Second International Conference on Materials Engineering for Resources, Akita, Japan, 19–22 October, 1994. Research Institute of Natural Resources attached to Mining College, Akitsa University, Japan. Sarja, A. (1995) ‘Methods and methodology on environmental aspects of building materials and structures’. RILEM Workshop on environmental aspects of building materials and structures, 21–22 September. Technical Research Centre of Finland: Espoo. Sarja, A. (1997) ‘A vision of sustainable materials and structural engineering’. In: Tuutti K. (ed.) Selected Research Studies from Scandinavia. Report TVBM-3078. Lund University, Lund Institute of Technology: Lund. Sarja, A. (1999) ‘Environmental design methods in materials and structural engineering— Progress Report of RILEM TC 172 EDM/CIB TG22’. Materials and Structures, 32, (December) 699–707. Sarja, A. (ed.) (2000) ‘Environmental design methods in materials and structural engineering: Integrated Life Cycle Design’, RILEM TC EDM/CIB TG22. Technical Research Centre of Finland: Espoo.

Introduction

Traditionally, design has concentrated on the construction phase of optimising construction costs and shortterm performance. Sustainable development gives rise to a need for integrated life cycle design, where all solutions are optimised for the entire design service life of the building. In the building, only the loadbearing frame, and most of the envelope are designed to resist degradation over the design service life. The parts having a shorter design service life, typically the building services, partitions and finishings, will probably be renewed several times during the design service life of the building. For these parts with shorter life cycles, recycling is both economically and ecologically important (Sarja 1997a). The other challenge for design is to guarantee the performance and durability of technical systems over the design service life. For this aim, durability design methods are important. Resistance design is expanded into durability design to include time as a new dimension in the design calculations (Sarja and Vesikari 1996). Health and safety aspects are generally related to the control of moisture and temperature conditions and to special areas such as hazardous emissions from materials. The definition already includes the principle that sustainability must always be treated according to the life cycle principle. In other words, the application of life cycle methodology to design, manufacture, construction, maintenance, and the management of building projects by companies and other organisations involved in building (Sarja 1997b). With regard to the design of materials and structures, this leads to the idea of integrated life cycle design, which is the subject of this book. The core competence and working area of structural engineers in the context of sustainable construction is the design of structures for sustainability over their entire life cycles. This means that the structural design process must be looked at anew. Furthermore, new methodologies and calculation methods must be adopted, for example from mathematics, physics, systems engineering and other natural and engineering sciences. However, we have to keep in mind the need of strong methodologies, and transparency and simplicity of the design process and its methods in order to keep these multiple issues under control and to avoid excessive design work. In life cycle design, analysis and design are expanded into two economic areas: financial costs and environmental costs. Life cycle costs are calculated as either present value or as annual costs by discounting the costs from manufacture, construction, maintenance, repair, changes, modernisation, rehabilitation, reuse, recycling and disposal. Monetary costs are treated, as usual, by current value calculations. Environmental costs are the use of non-renewable natural resources (materials and energy), and the production of air, water or soil pollution. The consequences of air pollution are health problems, inconvenience for people, ozone depletion and global warming. These impacts dictate the environmental profiles of the structural and building service systems. The goal is to limit the environmental costs to permitted values and to minimise them. Integrated lifetime design is an important link in construction: translating the requirements of owners, users and society into performance requirements of the technical

xi

systems; creating and optimising technical solutions, which fulfil those requirements; and proving through analysis and dimensioning calculations that the performance requirements will be fulfilled over the entire design service life. The adoption of these new methods and processes will increase the need for renewed education and training of all those involved. This new model of integrated life cycle design, also called lifetime design, includes a framework for integrated structural life cycle design, a description of the design process and its phases, and special lifetime design methods with regard to different aspects discussed above. Quality assurance has been widely systematised under the ISO 9000 standards. An environmental efficiency procedure is presented in the ISO 14000 standards. The impact of life cycle principles in construction is in the application of life cycle criteria in the quality assurance procedure. Multiple life cycle criteria are also applied during the selection of products, although most of the product specifications have already been produced at the design phase. Integrated life cycle design supports an improved quality approach, which can be called life cycle quality (see Figure 0.1). All the areas shown in Figure 0.1 are treated over the life cycle of structures, and controlled in the design by technical performance parameters. The life cycle performance of structures is highly dependent on maintenance. The first important instructions for life cycle maintenance are produced during the design stage. The structural system of a building or civil engineering facility needs a users’ manual, just like a car or any other piece of equipment. The manual will be produced gradually during the design process in co-operation with those involved in design, manufacture and construction. The usual tasks of the structural designer are: compiling a list of maintenance tasks for the structural system, compiling and applying operational instructions, control and maintenance procedures and works, checking and co-ordinating the operational, control and maintenance instructions of product suppliers and contractors, preparing the relevant parts of the users’ manual, and checking relevant parts of the final users’ manual. The active reduction of waste during construction, renovation and demolition is possible through the selective dismantling of structural systems, components and materials specifically for recycling. Selective dismantling includes detailed planning of the dismantling phases, and optimising the work sequences and logistics of the dismantling and selection process. The main goal is to separate the different types of materials and different types of components at the demolition phase in order to avoid multiple actions. The recyclability of the building materials and structural components depends on the degree and/or technical level of the desired reuse. References Sarja, A. (1996) ‘Environmental design methods in materials and structural engineering’. CIB Information, 4(96), 23–25. Sarja, A. (1997a) ‘A vision of sustainable materials and structural engineering’, in Tuutti K. (ed.) Selected Research Studies from Scandinavia. Report TVBM-3078. Lund University, Lund Institute of Technology: Lund. Sarja, A. (1997b) ‘Framework and methods of life cycle design of buildings’, Symposium: Recovery, Recycling, Reintegration, R’97, 4–7 February, Geneva. EMPA, VI, 100–105. Sarja, A. (1999) ‘Environmental design methods in materials and structural engineering— Progress Report of RILEM TC 172-EDM/CIB TG22’. Materials and Structures, 32 (December), 699–707. Sarja, A. and Vesikari, E. (1996) Durability Design of Concrete Structures. RILEM Report Series 14. E&FN Spon: London.

xii

Figure 0.1 Main aspects of life cycle quality (Sarja 1996, Sarja 1999)

1 Framework of integrated structural life cycle design

1.1 Scope and objectives Integrated structural design provides methods and methodologies for structural design to meet the requirements of sustainable development during the entire service life of structures, and thus to achieve a good life cycle quality. The scope of this book includes both loadbearing and non-loadbearing structures of buildings, bridges, towers, dams, harbours, tunnels and other structural facilities. This book includes: • • • •

definitions and terms framework schedule of the integral structural design systematics and central methods of the environmental structural design examples of applications in building and bridge design.

Architects, structural engineers, civil engineers, construction clients, and standards organisations are the target readers for this book. The objective for the development of environmentally-oriented design is to realise design methods and methodologies for structural design in order to meet the requirements of sustainable development during the entire life cycle of the structures (resources, transport, manufacture, use, recycling and reuse, demolition, waste disposal). Environmental design will be presented as a part of integrated structural design, which includes the mechanical, physical, economic, energy, health and safety, and environment aspects. Integrated design will manage these multiple requirements in a systematic way. 1.2 Standards and codes related to integrated life cycle design A number of general principles, and assessment and analysis methods, which serve as a basis for development of integrated life cycle design already exist. However, there is no consistent methodology which is only focused on the design of materials and structures, which is the subject of this book. The general framework of environmental management is defined in ISO 14000 standards: ISO 14001: ‘Environmental Management Systems. Specification with guidance for use’ and ISO 14004: ‘Environmental Management Systems. General guidelines on principles, systems and supporting techniques’. The role of this book is to provide design tools for fulfilment of the structural design issues defined in ISO 14004, Chapter 4.1 ‘Commitment and policy’ and Chapter 4.2 ‘Planning’. Product information about

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building materials and building components serve as an important information source of structural design. The following draft standards and committee drafts can be applied when evaluating environmental product information: ISO DIS 14040: ‘Environmental Management —Life Cycle Assessment—Principles and Framework’ and ISO 14041: ‘Environmental Management—Life Cycle Assessment—Inventory analysis’. Technical performance principles, and service life planning and prediction are treated in Draft International Standard ISO/DIS 15686–1. National methodology codes exist in several countries. Often their scope is more general than just building technology, but the methodologies are applicable with some modifications also in the building sector. Some national codes, standards and guidelines are listed in Appendixes 2 and 3. Comprehensive guidelines for integrated life cycle design of structures have been published by the Association of Finnish Civil Engineers (Sarja 2000b, 2001). 1.3 General features of environmentally efficient structural technology and design In ISO 14001 and 14004 the principle of a continued improvement process to achieve improvements in overall environmental performance is expressed. The environment is defined as the surroundings in which an organisation operates (including air, water, land, natural resources, flora, fauna, humans), and their interaction. Ecological aspects are the elements of an organisation’s activities, products or services that interact with the environment. Environmental impact is any change to the environment, whether adverse or beneficial, wholly or partially resulting from an organisation’s activities, products and services. Structural technology is a synthetic issue, where multiple requirements are fulfilled through the application of several basic technologies such as materials technology, manufacturing technology, information and automation technology. Structural design includes creative phases, analysis phases as well as optimisation and synthesis phases. In these phases there are also many solution methods. In the creative phase several innovation and brainstorming methods can be applied. The analysis and optimisation phase requires such skills as applied mathematics, physics, chemistry and even biology. The same methods used in design can also be applied to structural product development. Environmentally-efficient structural technology and design are the response to the goals defined in ISO 14004. The central problem in the development of sustainable structural technology and design is to recognise how the design process needs to be changed and which methods can be applied in order to realise the new kind of structural design which is needed. Ecology can be linked to the environmental costs. The term gives us quite a concrete starting point for the application of this aspect in structural engineering and design. Sustainability is related not only to ecology and economy, but also to all other groups of requirements, and it can be applied in the life cycle methodology of design, manufacturing, construction and management. Through the principle of sustainability, resistance design will be expanded into durability design, thus introducing time as a new dimension in design calculations (Sarja and Vesikari 1996). Consequently aspects of maintenance, changes during use, modernisation, renewal, repair, demolition, recycling and disposal need also to be added. Health and safey aspects are generally related to the control of moisture and temperature conditions and to special subjects such as noxious emissions from materials. Structural systems can be divided into assemblies having quite different requirements and environmental properties. Buildings and engineering structures have many aspects similar to each other, but they also differ in some respects. In buildings, energy consumption mostly dictates environmental properties. For this reason the thermal insulation of the envelope is important. The most important environmental aspects for structures with a long

FRAMEWORK OF INTEGRATED STRUCTURAL LIFE CYCLE DESIGN

3

target service life are flexibility with regard to functional changes and high durability, while for structures with a moderate or short target service life changeability and recyclabiiity are more important. The loadbearing frame is the most massive and longlasting part of the building. For the loadbearing frame, durability and flexibility to enable changes in the functions, spaces and services systems are most important. Internal walls have a moderate requirement of service life and may need to accommodate changes. For this reason internal walls must have good changeability and recyclability. An additional property of an environmentally effective structural system is good and flexible compatibility with the building services system, because the services system is the part of the building that is most often changed. During production it is important to apply effective recycling of production wastes in factories and on site. Finally there is the requirement to recycle the components and materials after demolition. Engineering structures such as bridges, dams, towers and cooling towers are often very massive and their target service life is long. Therefore environmental efficiency depends on the selection of environmentallyfriendly local raw materials, high durability and easy maintainability of the structures during use, recycling of construction wastes and finally recycling of the components and materials after demolition. Some parts of engineering structures, such as waterproofing membranes and railings, have a short or moderate service life and, consequently, easy re-assembly and recycling are most important. 1.4 Definition of integrated structural design The objective of the development of environmentally-oriented design is to realise design methods and methodologies for structural design in order to meet the requirements of sustainable development during the entire life cycle of the buildings. Environmental design will be presented as a part of integrated life cycle design, which includes the mechanical, physical, economic, energy, health and environmental aspects. The term ‘integrated life cycle design’ includes the design process, methodology and methods of design for life cycle quality, which aims to fulfil the multiple requirements of users, owners and society in an optimised way during the entire life cycle of a building or other built facility. 1.5 Content and schedule of integrated structural design Structural design is an important link in construction, translating the requirements of owners, users and society into performance requirements of the technical systems, creating and optimising technical solutions, which fulfil those requirements, and proving through analysis and dimensioning calculations, that the performance requirements will be fulfilled over the entire design service life. The framework of integrated design is presented in Figure 1.1. 1.6 Methodologies of life cycle design The integrated life cycle design methodology is aimed at regulating optimisation and guaranteeing the life cycle human conditions, economy, culture and ecology with technical performance parameters (Sarja 1994, 1995, 1996, 1997a, 1997b, 1997c, 1999a, 1999b, 2000a), as presented in Figure 1.2 (Sarja 2000b). With the aid of life cycle design we thus can optimise human conditions (health and safety, and comfort), and minimise financial costs and the environmental impacts. Through service life (performance and durability)

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Figure 1.1 Framework of integrated building design

design, the targeted service life can be guaranteed. The conceptual, creative design phase is decisive in using the potential benefits of integrated design process effectively. In this phase, the design is made on the system and module levels. Hierarchical modular systematics (Sarja 1989, Sarja and Hannus 1995) helps rational design, as the structural system typically has different parts or modules with different requirements, for example with regard to durability and service life requirements. In life cycle design, analysis and design are expanded into two economic areas: financial and ecological (environmental costs and impacts). Life cycle costs are calculated as the present value or as yearly costs by discounting the costs from manufacture, construction, maintenance, repair, changes, modernisation, reuse, recycling and disposal. Monetary costs are treated as usual in current value calculations. Environmental costs are the use of non-renewable natural resources and the production of air, water or soil pollution. The consequence of air pollution includes health problems, inconvenience to people, ozone depletion and global warming. These impacts dictate the environmental profiles of structural and building services systems. The goal is to keep environmental costs below permitted values and to minimise them The environmental impact profile generally includes the consumption of globally and locally critical raw materials such as energy and water and the production of CO2, CO, SO2, NOx, dust, solid wastes and noise. Environmental impact profiles are systematised in several approaches, such as ATHENA (Trusty and Paehlke 1994), the European Commission APAS-Programme report (Peuportier and REGENER Project

FRAMEWORK OF INTEGRATED STRUCTURAL LIFE CYCLE DESIGN

0 0.1 2 2.1 2.2 2.3

3

Design for Economy

3.1

Economic life cycle design of structural system and components

2.4 2.5 1 1.1

Design Process and Methods Integrated structural design and its applications Design for Performance Functional design of structural system and components Design for flexibility in use and in changes of the use Hygromermal design of structures Detailed design of structures Maintenance and repair design Control of Requirements and Specifications Multiple Criteria Optimisation and Decision Making

1.2

Service Life Planning of structures

1.3

Integrated design documentation Design for Health and Comfort Health aspects in design

5 5.1

4

5

Design for Ecology

4.1 Design for Energy Economy

4.2 Calculation of environmental burdens in manufacturing and construction 4.3 Design for reuse and recycling

Figure 1.2 Modules of the integrated life cycle design (Sarja 2000b)

1997) and BREEAM methodology (BREEAM 1990). A comprehensive description on existing life cycle assessment methods is reported by the United States Environmental Protection Agency (US EPA 1995). The basic principles are treated at a general level in several reports (Holmberg 1995). It is also critical to introduce time factors into the detailed structural design. This includes service life design to guarantee that the durability and performance of the structures meets corresponding target values (Sarja and Vesikari 1996, Sarja 2000c). Health impacts can be identified from medical knowledge and applied as criteria for structural design mainly in the areas of building physics and biology, including several hygrothermal and acoustical methods (Radünz 1998, Fava et al. 1992). 1.7 Factors of sustainability Generally speaking, the results of comparisons as regards ecological requirements, lead to the conclusion that differences between different materials and structural solutions during the construction phase are quite small. However, quite large differences can be found between life cycle sustainability factors of existing buildings or other facilities. These are caused by differences in the basic factors of sustainability: flexibility of design, buildability during the manufacturing and construction phase, adaptability to change during use,

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durability in comparison with the design service life and the recyclability of components with a quite short service life. Energy consumption in buildings is economically important and it dictates most of the environmental properties of a building’s life cycle, the differences in environmental costs between different structural systems is otherwise quite small. For example, in northern Europe the heating of buildings and provision of hot water and lighting produce, during a life cycle of 50 years, about 90 per cent of air pollutants, compared with only 10 per cent produced during the manufacturing of building materials, transport and construction. In warm and tropical countries the heating requirements are lower, but cooling buildings with air conditioning consumes even more energy than heating in cold climate countries. For this reason, as well as well-controlled heating, ventilating, cooling and heat recovery, the thermal insulation of the envelope is important. The loadbearing frame is the most massive and long-lasting part of the building, and its durability as well as its flexibility for future changes in use, layout and services provision are very important. The envelope needs to be durable and, as mentioned above, have effective thermal insulation and a safe static and hygrothermal behaviour. Internal walls have a more moderate service life, but they need to cope with relatively high degrees of change, and must therefore possess good adaptability and recyclability. An additional property of an environmentally-effective structural system is a good and flexible compatibility with the building services system, as the latter is the most frequently changed part of the building. In the production phase it is important to ensure the effective recycling of the production wastes in factories and on site. With regard to transportation systems, the life cycle energy efficiency of the entire traffic system is also of utmost importance. Civil engineering structures like bridges, harbours, roads, railways etc. are often very massive and their target service life is long (Sarja 2000d). Their repair works under use are difficult. Their life cycle quality is tied to high durability and easy maintainability during use, saving of materials and the selection of environmentally-friendly raw materials, minimising and recycling of construction wastes, and finally recycling of the materials and components after demolition. Some parts of the engineering structures like waterproof membranes and bridge railings have a short or moderate service life and therefore the aspects of easy re-assembly and recycling are most important. Technical or performance-related obsolescence of the transport system and its structures is a major reason for the demolition of civil engineering structures, which raises the need for the careful planning of the whole civil engineering system. We know that cost is the decisive factor in our society and budgets must always stay within agreed limits. Cost plays a major role when decisions between design alternatives are being made. 1.8 Energy efficient building concepts and specifications Heat energy consumption can be modelled as a function of the thermal insulation factors of the building envelope, interior ventilation and air leakage flow through the envelope. Thermal insulation factors include heat conduction through different parts of the envelope: walls, roof, floor, windows and doors. Ventilation includes the heat loss with exhaust air. Typical parameters of multi-storey apartment buildings in a north European climate are presented in Table 1.1.

FRAMEWORK OF INTEGRATED STRUCTURAL LIFE CYCLE DESIGN

7

Table 1.1. Thermal parameters defining levels of energy efficiency in buildings Class of energy efficiency Low energy efficiency Normal energy efficiency High energy efficiency (low energy building) Walls: k (W/m2 °K) Roof: k (W/m2 °K) Ground floor: k (W/m2 °K) Windows: k (W/m2 °K) doors: k (W/m2 °K) Vair, vent / hm2 living floor area k (W/m2 °K) Vair, leak / hm2 living floor area k (W/m2 °K) heat recovery efficiency of ventilation, r

1.00 0.80 0.80 4.00 3.00 0.50

0.30 0.25 0.30 2.00 0.70 1.25

0.15 0.15 0.15 0.80 0.30 1.25

1.50

0.50

0.10

0.0

0.0

0.60

References BREEAM (1990) Environmental Assessment Method. Building Research Establishment: Garston. Fava, J., Roy, F., Consoli, F., Denison, R., Dickson, K., Mohin, T. and Vigon, B. (eds) (1992) A Conceptual Framework for Life Cycle Impact Assessment. Society of Environmental Toxicology and Chemistry and SETAC Foundation for Environmental Education, Inc.: Sandestin, FA. Holmberg, J. (1995) ‘Socio-ecological principles and indicators for sustainability’. Dissertation, Institute of Physical Resource Theory, Chalmers University of Technology, University of Göteborg. ISO/DIS 15686–1. ISO TC 59/SC14. Guide for service life design of buildings. Draft standard. Peuportier, B. (coordinator), Kohler, N., Boonstra, C, Blanc-Sommereux, I., Hamadou, H., Pagani, R., Gobin, C. and Kreider, J. (1997) European Methodology for the Evaluation of Environmental Impact of Buildings: Life Cycle Assessment. REGENER Project, Final Report to European Commission DG 12, Brussels. Radünz, A. (1998) Bauprodukte und gebäudebedingte Erkrankungen. Springer Verlag: Berlin, Heidelberg. Sarja, A. (1989) Principles and Solutions of the New System Building Technology (TAT). Research Report 662. Technical Research Centre of Finland: Espoo. Sarja, A. (1994) ‘Development towards the ecological and recyclable building materials technology’. Second International Conference on Materials Engineering for Resources, 19–22 October, Akita. Research Institute of Natural Resources attached to Mining College, Akita University: Akita. Sarja, A. (1995) ‘Methods and methodology for the environmental design of structures’, RILEM Workshop on Environmental Aspects of Building Materials and Structures. Technical Research Centre of Finland: Espoo. Sarja, A. (1996) ‘Environmental design methods in materials and structural engineering’. CIB Information, 4(96), 23–25. Sarja, A. (1997a) ‘A vision of sustainable materials and structural engineering’, in Tuutti, K. (ed.) Selected Research Studies from Scandinavia. Report TVBM-3078. Lund University, Lund Institute of Technology: Lund. Sarja, A. (1997b) ‘Framework and methods of life cycle design of buildings’, Symposium: Recovery, Recycling, Reintegration, R’97, 4–7 February, Geneva. EMPA, VI, 100– 105. Sarja, A. (1997c) ‘Some principles of integrated structural design’, Structural Engineering International (SEI) 1/1997, 59–60. Sarja, A. (1999a) ‘Environmental design methods in materials and structural engineering’, Materials and Structures 32, (December), 699–707.

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Sarja, A. (1999b) ‘Towards life cycle oriented structural engineering’, in R.Eligehausen (ed.) Construction Material: Theory and Application. Ibüdem-Verlag: Stuttgart. Sarja, A. (2000a) ‘Integrated life cycle design as a key tool for sustainable construction’, in Sarja, A. (ed.), Integrated Life-Cycle Design of Materials and Structures ILCDES 2000. RILEM Proceedings PRO 14. RIL—Association of Finnish Civil Engineers: Helsinki. Sarja, A. (2000b) ‘Development towards practical instructions of life cycle design in Finland’, in Sarja, A. (ed.) Integrated Life-Cycle Design of Materials and Structures ILCDES 2000. RILEM Proceedings PRO 14. RIL— Association of Finnish Civil Engineers: Helsinki. Sarja, A. (2000c) ‘Durability design of concrete structures: Committee Report 130-CSL’. Materials and Structures/ Matériaux et Constructions, 33 (January-February), 14–20. Sarja, A. (2000d) ‘Design of transportation structures for sustainability’. 16th Congress of IABSE, Lucerne, Congress Report, and CD ROM. IABSE-AIPC-IVBH: Zurich and ETH-Hönggenberg. Sarja, A. (ed.) (2001) Lifetime Structural Engineering (in Finnish). Guidelines RIL 216– 2001. Finnish Association of Civil Engineers: Helsinki. Sarja, A. and Hannus, M. (1995) Modular Systematics for the Industrialised Building. VTT Publications 238. Technical Research Centre of Finland: Espoo. Sarja, A. and Vesikari, E. (1996) Durability Design of Concrete Structures. RILEM Report Series 14. E&FN Spon: London. Trusty, W.B. and Paehlke, R. (1994) Assessing the Relative Ecological Carrying Capacity Impacts of Resource Extraction. Forintek Canada Corp.: Vancouver. US EPA (1995) Life-Cycle Impact Assesssment: A Conceptual Framework, Key Issues, and Summary of Existing Methods. Report EPA-452/R-95–002 United States Environmental Protection Agency: Washington, DC.

2 Design process

2.1 Design tasks, methodology and methods Integrated structural life cycle design includes the tasks and methods in the design process shown in Table 2.1 (Sarja 1996, Sarja 2001). 2.2 Design process model Integrated structural life cycle design includes the following main phases of the design process (see Table 2.2): investment planning, analysis of the actual requirements, translation of the requirements into technical performance specifications of structures, creation of alternative structural solutions, life cycle analysis and preliminary optimisation of the alternatives, selection of the optimal solution between the alternatives and the detailed design of the selected structural system. The conceptual, creative design phase is decisive if the potential benefits of integrated life cycle design process are to be utilised effectively. In this phase, the design is made at a system level. Modular systematics helps rational design, because the structural system typically has different parts (here called modules) with different requirements with regard, for example, to durability and service life requirements (Sarja and Hannus 1995). The introduction of integrated principles into practical design is a wide-ranging process, where not only are the working methods of structural engineers changing, but also where co-operation between structural engineers, architects, building services system designers and other partners in construction and use has to be developed. Co-operation with clients and architects is especially important in order to utilise effectively the expertise of the structural engineers in the most decisive, creative and conceptual phases of the design. This type of co-operation also helps clients to realise the benefits of investing slightly more into structural design. Another important change in the design will be some kind of modularisation of the design, which means the separation of the designing of the functions, spaces and performance specifications from the designing of technical systems and modules. The first part of the design, which is performance oriented, will be made by the architect and technical designers in close co-operation with each other, as well as with the client and with users. The second part, which is a realisation

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Table 2.1 Integrated life cycle design process and central methods for application Design phase

Life cycle design methods

Investment planning

Multiple criteria analysis, optimisation and decisionmaking Life cycle (financial and environmental) costs Modular design methodology Quality function deployment (QFD) method Modular design methodology Quality function deployment (QFD) method Modular design methodology Quality function deployment (QFD) method Modular design methodology Modular design methodology Modular service life planning Life cycle (financial and environmental) costs calculations Modular design methodology Quality function deployment (QFD) method Multiple criteria analysis, optimisation and decisionmaking Design for future changes Design for durability Design for health Design for safety Design for hygrothermal performance Users’ manual Design for re-use and recycling

Analysis of clients’ and users’ needs Functional specifications of the buildings Technical performance specifications Creation and outlining of alternative structural solutions Modular life cycle planning and service life optimisation of each alternative Multiple criteria ranking and selection between alternative solutions and products

Detailed design of the selected solution

phase, is carried out by teams of technical designers and manufacturers working closely together. The realisation phase is often connected to contractors’ and supppliers’ specific building concepts. In this way the current problem of divergent design and manufacturing processes can be avoided without compromising the functional, performance and other requirements for the life cycle use of the building, which were discussed earlier. 2.3 Design phases These new aspects are widening the scope of the structural design and construction to the extent that the entire working process must be re-engineered. We can start to establish a new design process—integrated structural design—which will be described below. Starting from investment planning and analysis of owners’ and users’ needs and requirements, the structural engineer must be ready to work with the architect

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Table 2.2 Design phases, tasks and methods of integrated lifee cycle design Design phase

Tasks (possible tasks for structural engineers is shown in bold)

Investment planning

Define objectives of the building project. Define the study time period. Create alternative investment plans. Calculate life cycle (financial and environmental) costs (LCCs). Calculate cash flows of alternative plans. Evaluate benefits of the alternative plans. Compare LCCs and make final decision. Define final objectives. Analysis of clients’ and users’ needs Identify relevant attributes (customers’ requirements). Estimate the rate of importance of each attribute as weight. Functional specifications of the Translate the results of needs analysis buildings to demands. Identify relevant functional properties. Define weight of each property. Technical performance specifications Translate functional properties and their weights from previous task to demands. Identify technical performance properties. Identify weight of each property. Creation and outlining of alternative Create and outline alternative structural solutions solutions for building, its structural systems and building services in cooperation with other designers and project partners.

Life cycle design methods

Multiple criteria analysis, optimisation and decision-making.

Life cycle financial and environmental costs.

Modular design methodology. Quality function deployment (QFD) method. Modular design methodology. Quality function deployment (QFD) method. Modular design methodology.

Quality function deployment (QFD) method. Modular design methodology.

(continued…) Table 2.2 (continued) Design phase

Tasks

Life cycle design methods

Modular life cycle planning and service life optimisation of each alternative

Define the requirement for design service life of the building.

Modular design methodology.

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Design phase

Multiple criteria ranking and selection between alternative solutions and products

Detailed design of the selected solution

Tasks

Life cycle design methods

Divide the building into service life modules with different service life classes. Identify the number of life cycles of each module during the design service life of the building. Identify the design life cycle costs (monetary and enviromental) of the modules. Outline alternative service lifes for the modules. Define optimal service lifes for the modules, based on minimum total costs (financial and environmental). Transfer the optimised service life cost of each alternative building concept from previous tasks. Define multiple attributes from analysis of owners’ and users’ requirements. Evaluate the performance properties of each alternative. Select the alternative for realisation between the alternatives. Design the structural modules for different performance requirements.

Modular service life planning.

Life cycle (financial and environmental) costs calculations.

Modular design methodology.

Quality function deployment (QFD) method. Multiple criteria analysis, optimisation and decision-making.

Design for future changes. Design for durability.

Make the synthetic design. Design for health. Design for safety. Design for hygrothermal performance. Users’ manual. Design for reuse and recycling.

and other partners in the building process. Controlled and rational decision-making when optimising between the many requirements with different measurement systems is possible through the use of multiple criteria decision-making. Environmental and health and safety aspects are are given more weight. Service life principles introduce time as a variable in economics and design. 2.3.1 Investment planning The owner/client defines life cycle objectives such as area and functional requirements of building and its spaces, economics, requirements for use, service life, aesthetic objectives and ecological objectives.

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Designers in co-operation with the owner create alternative investment plans, and make a multiple criteria analysis leading to decision-making between alternatives. 2.3.2 Analysis of clients' and users' needs The analysis of clients’ needs is a preparatory phase of the building project. This phase deals mainly with the use and the spatial requirements of the buildings, and it is the responsibility of the client, the architect and the contractor. Usually the structural designer is not involved in this analysis, but provides technical support for the architect and uses the results as a starting point for his own work. 2.3.3 Translation of the clients' and users' needs into functional life cycle requirements of the buildings The quality function deployment (QFD) method can be applied as a means of analysis when ranking the functional properties of draft design alternatives in comparison to the owners’ and users’ needs. The architect has main responsibility of this phase, and the structural engineer provides technical support and expertise and is possibly involved in calculations connected with the analysis. 2.3.4 Translation of the functional life cycle requirements into technical performance specifications The results of the functional analysis and planning will be converted into structural requirements in cooperation between the architect and the structural designer. The result is a set of technical specifications, including mechanical, physical, aesthetic, environmental, energy and health specifications. The performance specifications are presented in detail in ISO 6240–1980: ‘Performance standards in building—Contents and presentation’ and ISO 6241–1984: ‘Performance standards in building—Principles for their preparation and factors to be considered’. Once the clients’ needs have been properly defined and translated into functional requirements, they must be expressed as performance specifications. They should, as far as possible, be quantitative and preferably related to well-established (standardised) test methods. However, these methods are only available to a limited extent and consequently performance requirements must be given in other forms. Often the requirements are described only in qualitative terms. Requirements or ‘target figures’ for heating and cooling energy needs are given in some cases, as well as financial figures such as annual costs for the building or its sub-systems. Modular scheduling and allocation at the conceptual design phase includes the specification of the alternative structural solutions with regard to the target service life and technical performance requirements of each structural module. Based on the specifications, estimates of lifetime financial and environmental costs as current values or annual costs are calculated. The model for the modular specification of the technical performance properties is presented in Table 2.3. The specification work must interact with life cycle optimisation of the central properties in order to reach the target of optimal design (ASTM 1995, CEN 1997).

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2.3.5 Creation and outlining of alternative structural solutions The phase of conceptual design is the most important, because the decisions made in this phase have a strong influence on the economic, environmental, aesthetic, functional and technical quality of structures. The role of structural designer in this phase is to support decision-making by the owner and users. The main tools in this work are creative structural drafting, analysis, optimisation, and multiple criteria decisionmaking described above. The role of the architect is very similar to that of the structural designer, but the tools are more weighted towards creative functional and aesthetic areas. Close co-operation between the structural designer, the architect and building services designers is needed. Living and working demands on spaces and other functional requirements of buildings are changing more and more rapidly. The future value of buildings is largely dependent on their flexibility for changes in use. The structural system and its compatibility with the building services system are decisive factors for adaptability of a building. Starting as early as the sketch design, design for change is one of the central aims. Important issues in conceptual design are: • sufficient storey height to allow for changes in services installations • long spans of floorings which do not prevent changes in use because of too many vertical loadbearing structures • location of openings in facades • spaces for staircases (connection modules) for traffic, and for horizontal and vertical connections of building services systems • space for horizontal piping and wiring • room sizes large enough for alternative uses • easily moveable and reusable partition walls • easily changed electrical and communication wiring systems. Table 2.3 Specification of performance properties for alternative structural solutions at a module level using a multistorey apartment building as an example Structural module

Central performance properties in specifications

Foundations

Loadbearing capacity, target service life, limits and targets for environmental impact profiles. Loadbearing capacity, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles. Target values for thermal insulation, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles. Target values for thermal insulation, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles. Target values for thermal insulation, target service life, estimated repair intervals, estimated maintenance costs, limits and targets of environmental impact profiles. Target values for thermal insulation, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles. Target values for thermal insulation, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles.

Loadbearing frame Envelope/walls Envelope/roof Envelope/ground floor Envelope/windows Envelope/doors

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Structural module

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Central performance properties in specifications

Partition floors

Target values for sound insulation, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles, estimated intervals of the renewal of connected building service installations. Partition walls (including doors) Target values for sound insulation, target service life, estimated intervals of spatial changes in the building, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles, estimated intervals of the renewal of connected building service installations. Bathrooms and kitchens Target values for sound and moisture insulation, target service life, estimated repair intervals, estimated maintenance costs, limits and targets of environmental impact profiles, estimated intervals of the renewal of connected building service installations.

2.3.6 Modular life cycle planning and service life optimisation For life cycle planning, a modular methodology is preferred. This allows the systematic allocation and optimisation of the target service life as well as life cycle economy and ecology of different parts of the building (ASTM 1995, CEN 1997). A suitable modularisation at the highest level of hierarchy is as follows: loadbearing frame, envelope, foundations, partitions, heating and ventilating services, information, water and sewage systems, control services and waste management systems. All of these systems are specified during the development or design process with continuously increasing precision starting from general performance specifications and ending with detailed designs. The following tasks are required for each design alternative: • classification of building modules into target service life classes, following a suitable classification system.; • defining the number of times each module must be renewed or replaced during the design service life of the building; • calculation of total life cycle financial and environmental costs during the design life cycle of the building; • preliminary optimisation of the total life cycle cost by varying the value of service life of key modules in each alternative within permitted values. The division of the building into modules can be the same as that presented in Section 2.3.5. After the life cycle financial and environmental costs of alternative designs have been calculated, they are transferred into multiple criteria ranking and selection between alternative designs made. 2.3.7 Ranking and selection between design alternatives and products The ranking of design alternatives ends the sketch design phase and results in the draft designs. Even in the sketch design phase, the selection of some key products which are connected to solutions of the structural system may have been partly completed; although the selection of products is mainly done at later phases of the design. When applying integrated design procedures, all classes of requirements are systematically taken

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into account during the ranking. Multi-attribute decision analysis (MADA) is used as a ranking method (ASTM 1995, Roozenburg, and Eekels 1990, Sarja 1999a, Sarja 2001). Core properties are principally calculated quantitatively with numerical values, but some additional properties are only evaluated qualitatively. The properties are normalised by comparison with a reference alternative. This phase of design is usually the responsibility of the architect who is supported by the structural designer and the designers of building services systems. An example of a multiple-attribute decision-making procedure in design is presented in Figure 2.1. 2.3.8 Detailed design of the selected solution The role of detailed design phase is to ensure that the targets and specifications defined in the conceptual design can be realised in construction and throughout the building’s life cycle. This means the structure must be buildable, serviceable, durable, that it can be maintained and repaired, and finally that it can be demolished and the waste recycled or disposed of. The methods used at this phase include: structural mechanics, building physics (moisture and thermal calculation methods, and methods of acoustics and fire resistance) and durability design. The detailed design includes generally the following phases: 1 ordinary mechanical design 2 durability design 3 final design. Ordinary mechanical design is performed using conventional design methods. Its purpose is to determine the preliminary dimensions for the structure. The durability design procedure is different for structures made from different materials. With concrete structures, most often a basic procedure can be applied. Usually the durability design procedure for steel structures also follows a general procedure. The durability of wooden structures is connected to moisture and temperature and thus leads to the moisture control of structures in order to eliminate the danger of the wood rotting. When using deterioration calculation models, the design procedure for wooden structures also follows the general procedure. A flow chart of the design procedure, with the design of concrete structures as an example, is presented in Figure 2.2 2.3.8.1 Static, dynamic and seismic design Mechanical design includes the static, fatigue and dynamic design aspects. This design is traditional and many manuals, guides, norms and standards exist, therefore this phase will not be discussed any further in this context.

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Figure 2.1 Multiple-attribute decision-making procedure

2.3.8.2 Durability design for service life The role of durability design is important in life cycle design. The objective of durability design is to ensure that the specified target service life can be achieved in the actual working environment of the structure. In ordinary design the durability for ordinary service life, generally for 50 years, is taken into account through the structural detailing rules found in norms, standards and design manuals. When using a target service life other than 50 years separate service life design calculations are needed. For these specific purposes statistically-based service life design methods can be used to produce specific detailing rules and model designs which then can be applied for similar specific cases. Statistically-based life cycle design can also be applied in the product development of prefabricated structural units.

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The detailed durability design procedure is as follows (Sarja and Vesikari 1996, Sarja 2000b, Sarja 1997b): 1 2 3 4 5 6 7

specification of the target service life and design service life analysis of environmental effects identification of durability factors and degradation mechanisms selection of a durability calculation model for each degradation mechanism calculation of durability parameters using available calculation models possible updating of the calculations of the ordinary mechanical design (e.g. own weight of structures) transfer of the durability parameters into the final design. LIFETIME SAFETY FACTOR METHOD

The lifetime safety factor design procedure is somewhat different for structures consisting of different materials, although the basic design procedure is the same for all kinds of materials and structures. The lifetime safety factor method is analogous with the safety factor method of static design, also known as limit state design. The lifetime factor design procedure is as follows: 1 2 3 4 5 6 7

specification of target service life and design service life analysis of environmental effects identification of durability factors and degradation mechanisms selection of a durability calculation model for each degradation mechanism calculation of durability parameters using available calculation models possible updating of calculations of the ordinary mechanical design (e.g. own weight of structures) transfer of durability parameters into final design. STATISTICAL DURABILITY DESIGN

The simplest mathematical model for describing the ‘failure’ event comprises a load variable S and a response variable R (Sarja and Vesikari 1996). In principle the variables S and R can be any quantities and expressed in any units. The only requirement is that they are commensurable. Thus, for example, S can be a weathering effect and can be the capability of the surface to resist the weathering effect without unacceptably large visual damage or loss of the reinforcement concrete cover. If R and S are independent of time, the ‘failure’ event can be expressed as follows (Sarja and Vesikari 1996): (2.3) The failure probability Pf is now defined as the probability of that ‘failure’: (2.4) Either the resistance R or the load S or both can be time-dependent quantities. Thus the failure probability is also a time-dependent quantity. Considering R( ) and S( ) are instantaneous physical values of the resistance and the load at the moment the failure probability in a lifetime t could be defined as: (2.5a)

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Figure 2.2 Flow chart of the durability design procedure, concrete structures as an example (Sarja and Vesikari 1996, Sarja 2000a)

The determination of the function Pf(t) according to the Equation 2.5a is mathematically difficult. That is why R and S are considered to be stochastic quantities with time-dependent or constant density distributions. By this means the failure probability can usually be defined as: (2.5b) According to the Equation 2.5b the failure probability increases continuously with time as schematically presented in Figure 2.3. Considering continuous distributions, the failure probability Pf at a certain moment of time can be determined using the convolution integral: (2.6) where FR (s) is the distribution function of R, fs (s) the probability density function of S, and s the common quantity or measure of R and S.

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Figure 2.3 The increase of failure probability: illustrative presentation (Sarja and Vesikari 1996)

The integral can be approximately solved by numerical methods. The statistical method can, in principle, be used for individual special cases even in practice, but this will not find any common use. The main use of statistical theory is in the development of deterministic methods. Such a method is the lifetime safety factor method presented above. 2.3.8.3 Hygrothermal design In many countries, modern building has demonstrated significant problems associated with the indoor climate. The expression ‘sick building syndrome’ (SBS) is used to characterise the problem. Much research has been performed in order to clarity the mechanisms, but the final answer has not yet been found. Drastically increased thermal insulation and airtightness of buildings following the first so-called oil crisis in 1973, when energy prices increased rapidly, is often blamed for the problems. However, it seems obvious that moisture content and transport in materials and in building components play an important role. The wellknown problems in connection with foundation systems using concrete slabs directly on the ground and crawl space foundations could exemplify this. As moisture dynamics are closely related to, and very often impossible to separate from, thermal mechanisms it is obvious that the hygrothermal analysis of the building should be undertaken. Design methods are available today for the most important performance requirements, but it must be stated that they are not accurate as those used, in strength and deformation analysis. One reason for this is that the measurement of material properties is, in many respects, much more difficult, especially concerning moisture transport. Much of the basic physics has not been fully clarified. Important material properties in the hygrothermal analysis are: • • • • • • •

heat conductivity specific heat thermal diffusivity vapour resistance moisture diffusivity capillarity sorption curves (relative humidity versus moisture content at equilibrium).

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The hygrothermal design of a building contains the following major steps: • definition of building context • clarification of thermal and moisture environment (boundary conditions) • analysis of temperatures and moisture status in different parts of the structure, account being taken to non-steady state conditions. • definition of critical temperature and moisture levels • comparison of actual and critical values • accepting/rejecting the proposed solution. 2.3.8.4 Acoustic design Acoustic design usually includes airborne sound insulation, impact noise level control between spaces and control of vibrations of structures during use. Sound insulation is usually controlled through standards on sound insulation and vibrations, but special rules and calculation methods (e.g. for flooring) also exist. In special cases (e.g. concert halls and theatres), the internal sound acoustics are a primary requirement. This is a job for specialised experts and is not dealt with in detail here. 2.3.8.5 Design for safety Static and dynamic safety as well as fire safety are defined in international and national regulations, norms and standards dealing with traditional methods of mechanical design. Because these design methods are standard, they are not discussed here. Integrated life cycle design provides a new viewpoint on safety by a systematic consideration and optimisation of long-term safety, taking into account degradation effects. 2.3.8.6 Design for health Health requirements can follow the guidelines of SETAC (Fava et al. 1992) and other national and international codes, standards and guides. The main issues are to avoid moisture in structures and on finishing surfaces, and to check that no materials used cause emissions or radiation which are dangerous for health and comfort of the users (Radünz 1998). In some areas radiation from the ground must be also be eliminated though insulation and ventilation of the foundations. Thus the main tools for health design are: selection of materials (especially finishing materials), eliminating risks of moisture in structures (through waterproofing, drying during construction and ventilation), and elimination of possible radioactive ground radiation with airproofing and ventilation of ground structures (Sarja 2001, Sarja 2000a). 2.3.8.7 Design for reuse and recycling The environmental profile of basic materials already includes recycling efficiency, which means the environmental cost of recycling. It is important to recognise that the recycling potential of building components, modules and even technical systems need to reconsidered in connection with design. The

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higher the hierarchical level of recycling, the higher also the ecological and economic efficiency of recycling (Lippiatt 1998, Sarja 1999). Designers can influence reuseability and recyclability through the choice of the structural system, component types and their connections, and through the choice of materials. Modules and components can be divided into different classes of reuseability and recycleability through performance and service life based modular systematics. Typically modules and components with a short service life or high likelihood of change should have a good potential for reuse or recycling. Modules and components which have a long service life, typically the loadbearing frame, must allow the layout of building spaces to be easily changed, and they must have a long service life and good maintainability. Special issues to be considered in the design of structures and materials for reuse and recycling are: • modular structural system with autonomous modules with a dimensional and modulation and clear tolerance system (Sarja 1989, Sarja and Hannus 1995) • separability of the structural components or materials during demolition of building (e.g. through the use of demountable structural components using suitable connections and joints) • constructive separation of technical systems (e.g structures and building services systems) with different service lives and different recycling techniques • reduction in the variety of materials • ability to separate materials, which cannot be recycled together • avoiding insoluble composite substances and/or composite substances that are either only slightly soluble or soluble only within a high expenditure or energy input. 2.3.8.8 Users’ manual and maintenance plan A building, like a car or other equipment, needs a users’ manual. The manual will be produced gradually during the design process in co-operation between the partners in design, manufacture and construction. The usual tasks of the structural designer include: • collecting lists of maintenance tasks for the structural system • collecting and applying instructions for operation, control and maintenance procedures and works • checking and co-ordination of operation, control and maintenance instructions of product suppliers and of the contractor • preparing the relevant parts for the users’ manual • checking the relevant parts of the final users’ manual. The main information sources for the users’ manual are product descriptions from producers, which have to include relevant information on all classes of technical performance, service life, maintenance tasks and their frequency, and health aspects. Information on the environmental impact profile, resue and recycling should also be included in the product description. The users’ manual is a link between design and maintenance, thus paving the way towards real life time engineering (Sarja 1999b).

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2.2.8.9 Final integration of design specifications Design specifications which are produced at different phases of the design process are collected together during the design process, co-ordinated and checked to avoid differences in details and specifications. This co-ordination is a continuing task during the design period and it finally produces the documentation for building control and maintenance during the building’s life cycle. References ASTM (1995) Standard Practice for Applying the Analytic Hierarchy Process to Multi-attribute Decision Analysis of Investments Related to Buildings and Building Systems. ASTM Designation E 1765–95. CEN (1997) Concrete: Performance, Production and Conformity. Draft prEN 202. European Committee for Standardisation (CEN): Brussels. Fava, J., Roy, F., Consoli, R, Denison, R., Dickson, K., Mohin, T. and Vigon, B. (eds) (1992) A Conceptual Framework for Life Cycle Impact Assessment. Society of Environmental Toxicology and Chemistry and SETAC Foundation for Environmental Education, Inc.: Sandestin, FA. Lippiatt, B. (1998) ‘Building for Environmental and Economic Sustainability (BEES)’. CIB/RILEM Symposium: Materials and Technologies for Sustainable Construction, Gävle, June. Building and Fire Research Laboratory, National Institute of Standards and Technology: Gathersburg, MD. Radünz, A. (1998) Bauprodukte und gebäudebedingte Erkrankungen. Springer Verlag: Berlin, Heidelberg. Roozenburg, N. and Eekels, J. (1990) EVAD, Evaluation and Decision in Design. (Bewerten und Entscheiden beim Konstruiren). Schriftenreihe WDK 17, Edition HEURISTA: Zürich. Sarja, A. (1989) Principles and Solutions of the New System Building Technology (TAT). Research Report 662. Technical Research Centre of Finland: Espoo. Sarja, A. (1996) ‘Environmental design methods in materials and structural engineering’. CIB Information, 4(96), 23–25. Sarja, A. (1997b) ‘Framework and methods of life cycle design of buildings’. Symposium: Recovery, Recycling, Reintegration, R’97, 4–7 February, Geneva. EMPA, VI, 100–105. Sarja, A. (1999a) Environmental Design Methods in Materials and Mtructural Engineering —Progress Report of RILEM TC 172-EDM/CIB TG 22. Materials and Structures, Vol. 32, December 1999, 699–707. Sarja, A. (1999b) ‘Towards life cycle oriented structural engineering’, in Eligehausen, R. (ed.) Construction Materials: Theory and Application. Ibiidem-Verlag: Stuttgart. Sarja, A. (2000a) ‘Development towards practical instructions of life cycle design in Finland’, in Sarja, A. (ed.) Integrated Life-Cycle Design of Materials and Structures ILCDES 2000. RILEM Proceedings PRO 14. RIL— Association of Finnish Civil Engineers: Helsinki. Sarja, A. (2000b) ‘Durability design of concrete structures: Committee Report 130-CSL’. Materials and Structures/ Matériaux et Constructions, 33 (January-February), 14–20. Sarja, A. (2001) Lifetime Structural Engineering (in Finnish). Guidelines RIL 216–2001. Finnish Association of Civil Engineers: Helsinki. Sarja, A. and Hannus, M. (1995) Modular Systematics for the Industrialised Building. VTT Publications 238, Technical Research Centre of Finland: Espoo. Sarja, A. and Vesikari, E. (1996) Durability Design of Concrete Structures. RILEM Report Series 14. E&FN Spon: London.

3 Life cycle design methods

3.1 Classification of design methods Life cycle quality as defined earlier in the text and Figure 0.1 in the Introduction, can be implemented in design with different types of methods and principles. A classification of these methods is presented in Figure 3.1. Life cycle design methods are tools to guarantee life cycle quality in design. The design methods can be classified in relation to the factors of life cycle quality as presented in Table 3.1. The methods shown in Figure 3.1 and Table 3.1 are mainly applied to design of buildings. The conceptual, creative design phase is decisive in ensuring that the potential benefits of the integrated design process are utilised effectively. These include traffic system planning and long-term optimisation, starting from regional planning and the planning of urban areas. Controlled and rational decision-making when optimising multiple requirements with evaluation criteria is possible through the application of systematic multiple attribute optimisation and decision-making. In the detailed design phase, life cycle aspects emphasise the need for total performance over the life cycle, including durability design and design for mechanical and hygrothermal performance. The incorporation of integrated design principles into practical design is a fairly extensive process, in which not only is the work of the structural engineers changing, but also co-operation has to be developed between structural engineers and other partners in construction and use. A modularisation of the design— the separation of the functional design and performance specifications from the detailed design of structural systems and modules—will be needed. The first part of the design process is performance-oriented. The second part is created by a close team of technical designers and contractors. In this way the current problem of diversified design and manufacturing processes can be avoided without compromising functional and performance requirements. This book focuses on those methods which are non-traditional and which fall within structural engineers’ areas of expertise. Consequently, design of heating, ventilating, cooling and lighting systems as well as aesthetic design are not dealt with here, as they fall outside these areas of expertise. The usual areas of structural design: static, dynamic, seismic, hygrothermal and fire safety design have been mentioned only briefly, because they are a traditional area of structural design.

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Figure 3.1 Classification of design methods of integrated life cycle design Table 3.1 Design methods for different types of requirements of buildings Requirement class

Design method

Functionality in use

Analysis of clients’ needs. Multi-attribute analysis and decision-making. Quality function deployment method (QFD). Modular functional spatial planning. Design for changes in use. Modular service life planning and optimisation.

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Requirement class

Design method

Financial considerations

Life cycle costing. Modular design methodology. Multiple-attribute optimisation and decision-making Modular service life planning and optimisation Service life design Environmental life cycle analysis and costing. Modular design methodology. Design for energy efficiency. Design for recycling and reuse. Multi-attribute optimisation and decision-making. Static design. Dynamic design. Service life and durability design. Seismic design. Fire safety design. Hygrothermal design. Health checking of materials and materials combinations. Health classification of internal climate. Design of heating, ventilation, cooling and lighting. systems for healthy interior conditions. Design for acoustic comfort. Design for comfortable internal climate. Design for aesthetic comfort. Aggregation of life cycle performance parameters. Multi-attribute analysis and decision-making.

Environmental considerations

Safety

Health

Convenience

Integration of design solutions

In the design process of civil engineering structures some special viewpoints have to be taken into account. The main phases of the life cycle design procedure of a transportation system are: regional planning, planning of traffic and transport systems, investment planning, analysis of the actual requirements, translation of the requirements into technical performance specifications for structures, the creation of alternative structural solutions, life cycle analysis and preliminary optimisation of the alternatives, selection of the optimal solution between the alternatives, and finally the detailed design of the selected system and its structures. A summary of the integrated life cycle design phases and the specific design methods are presented in Table 3.2. Table 3.2 Integrated life cycle design process and central methods for application in civil engineering Design phase

Life cycle design methods

Regional planning, planning traffic and transport systems, investment planning

Multiple criteria analysis, optimisation and decisionmaking. Life cycle financial and environmental costs. Multiple criteria analysis, optimisation and decisionmaking. Quality function deployment method (QFD). Multiple criteria analysis, optimisation and decisionmaking. Quality function deployment method (QFD).

Analysis of users’ and society’s requirements

Functional specifications and service life planning

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Design phase

Life cycle design methods

Technical performance specifications Creation and outlining of alternative solutions Service life planning and service life optimisation

Performance-based methodology. Modular design methodology. Modular design methodology. Modular service life planning. Life cycle financial and environmental cost calculations. Modular design methodology. Multiple criteria analysis, optimisation and decisionmaking. Design for future changes. Design for durability. Design for safety. Design for multiple requirements performance. Design for health and comfort. User’s manual. Design for re-use and recycling.

Multiple criteria ranking and selection between alternative solutions Detailed design of the selected solution

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3.2 Modular design methodology Open modular systematics includes modularisation of products, organisation and information, dimensional co-ordination, tolerance system, performance-based product specifications, product data models etc., so that the suppliers provide products and service modules that will fit together. Openness is a concept with many aspects, for example • • • • •

opennness to competition between suppliers openness for alternative assemblies openness to future changes openness to information exchange opennnes for integration of modules and subsystems.

At all phases of the life cycle of a building, the hierarchical modular product systematics of the building can be applied (see Figure 3.2). Modular systematics can be used to divide different parts of the building into different classes of service life. Typically the loadbearing frame represents a long-term service life, which has to be flexible to changes in the use and space allocation in the building. The floors also serve as the horizontal distributors of building services systems, and compatibility between the floors and the building’s installations is extremely important. The overall product system aims to create an entire building from interacting parts. The system can thus be defined as an organised whole consisting of parts, the relations between which are defined by rules. Compatibility can be achieved either through flexible integration or through separation of the structure and its installations. The envelope usually also has a requirement of a long service life and of good maintainability and repairability. Partition walls need to be altered when functional spaces are changed. In addition, partition walls are important locations of building services systems. The most concentrated service distribution parts of the building are the connection modules, which include the staircase, lift, vertical piping and wiring, horizontal distributing connections for service systems and possibly distributed building services equipment. It is important to develop building services systems (heating, ventilating, cooling, water

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Figure 3.2 Overview of the hierarchical modular building product system (Sarja 1989, Sarja and Hannus 1995)

and sewage, electrical, information and communication, and waste management) according to modular principles, taking into account especially the interaction and compatibility with the structural system. Building services functions can be distributed by the technical services systems in innovative ways, for example, by combining heating, cooling and ventilating together with a computerised operational control system into an integrated module. The systematics will be presented as model designs, alternative organisational models and applied product data models. It is important to identify and analyse productivity so that the results can then be used in the development of methods to improve productivity. In modular design, modularisation involves division of the whole into subentities, which are to a significant extent compatible but independent. Compatibility makes it possible to use interchangeable products and designs which can be joined together according to connection rules to form a functional whole building or other structural system. Typical modules in a building are: • • • • •

loadbearing frame facades roofing system partition walls building services systems.

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Typical modules of a bridge are: • • • • • • • •

foundations (including pilings) supporting vertical structures bearing horizontal structure deck deck waterproofing pavement edge beams railings.

Modular product systematics is connected to the performance systematics of the building. For example, the main performance requirements of floors can be classified in the following way: 1 Mechanical requirements, including • static loadbearing capacity • serviceability behaviour: deflection limits, cracking limits and damping of vibrations. 2 Physical requirements, including • • • • •

air tightness acoustics: airborne sound insulation, impact sound insulation, emission moisture tightness (in wet parts of the floor) thermal insulation between cold and warm spaces fire resistance and fire insulation.

3 Flexible compatibility with connecting structures and installations. • partitions • services: piping, wiring, heating and ventilating installations. 4 Other requirements: • buildability • changeability during the use • easy demolition, reuse, recycling and wasting.

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3.2 Life cycle costs 3.2.1 Financial and environmental costs Future costs are calculated by estimating annual costs, recurring costs and their frequency and finally discounting future costs into current values. Annual and recurring costs can be estimated simply as an addition of the relevant costs: construction costs, operation costs, maintenance costs, change costs, and repair, restoration and renewal costs. The costs of demolition, reuse, recycling and waste disposal can even be included. All these costs are discounted into current value, or calculated as annual costs. As an example, the estimation of the future design service life costs of the alternative structural solutions of bridges is based on the specifications given in Table 3.3. In order to calculate life cycle costs, the frequency of maintenance, changes, repairs, restoration and renewal must be known. Table 3.3 Specification of performance properties for the alternative structural solutions on a module level; as an example a bridge Structural assembly

Central performance properties in the specifications

Substructures (foundations, retaining walls)

Loadbearing capacity, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles Loadbearing capacity, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles Target values for moisture insulation, target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles, estimated intervals for renewal Target service life, estimated repair intervals, estimated maintenance costs, limits and targets for environmental impact profiles, estimated intervals for renewal

Vertical and horizontal superstructures (loadbearing structural system) Deck overlayers (waterproofing, pavement)

Installations (railings, lights)

3.2.2 Calculating present values of life cycle financial and environmental costs The building incurs financial and environmental costs during its entire life cycle starting from the planning phase and ending at recycling or waste disposal after demolition. The cost process, from which both monetary and environmental costing calculations can can be produced, is shown in Figure 3.3. Life cycle costs are calculated using the usual current value discounting method, which is applied to both the financial and environmental costs, using the following equations (3.1) where Etot is the design life cycle monetary cost as a present value td design life

LIFE CYCLE DESIGN METHODS

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E(0) construction cost N(t) coefficient for calculation of the current value of the cost at the time t after construction E(t) cost to be borne at time t after construction. Er(t) residual value at time t (3.2) where Eetot(td) is total life cycle environmental cost in relevant terms Ee(0) environmental cost at the construction phase Ee(t) environmental cost to be borne at time t after construction kr efficiency factor of recycling at renewal of each product The time coefficient N(t) can be calculated using the equations (3.3) where i is the interest rate n the time (years) from the date of discounting For the ecological calculations the expenses are environmental burdens, for example, consumption of non-renewable raw materials and energy, and the production of pollutants into the air, soil and water, including CO2, CO, SO2, NOx, dust and solid wastes. It is also recommended that a virtual rate is used when calculating the current value of future environmental costs, because future technology is assumed to be more environmentally effective than the current technology. The coefficients N(t) and Ns can either be calculated from known equations or taken from general financial calculation tables. The life cycle costs can be used both for optimisation and as a selection criteria between design alternatives and products. The components of the ecological costs are: consumption of non-renewable raw materials and energy, the production of pollutants into air, soil and water, including CO2, CO, SO2, NOx, dust, solid wastes and noise, and the loss of biodiversity. Integrated environmental implications such as the ‘greenhouse effect’, ‘acidity effect’ or ‘oxidants effect’ can be used instead of individual environmental impact (Udo de Haes et al. 1999). It is also recommended that a virtual rate is used when calculating the current value of future environmental costs, because future technology is assumed to be more environmentally effective than the current technology. Proposed rates in the discounting of future costs into present values are as follows: Real interest rate to be used in Cost to society Cost to firms and individuals

Financial costs (%) 2 3–5 (10)

Environmental costs (%) 1–2 (5) 1–2 (5)

The rates in parentheses are extreme values, which should only be used in special cases. For the enviromental calculations the rate describes the estimated speed of development in environmental efficiency of technologies. An ordinary rate of development would be represented by 1 per cent, 2 per cent in the case of rapid development being estimated and 3 per cent for special cases where rapid changes in technology are assumed. As examples, the proposed rates lead to the following values of the coefficient N(t):

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Figure 3.3 An environmental life cycle costing scheme

Time from construction (years)

N(t), the annual rate r being

10 20 30 50 100

1% 0.90 0.82 0.74 0.61 0.37

3% 0.74 0.55 0.41 0.23 0.052

5% 0.61 0.38 0.23 0.087 0.009

10% 0.38 0.15 0.057 0.009 0.000

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There are also aspects, such as biodiversity, which cannot be calculated numerically. These can only be evaluated qualitatively and descriptively. In qualitative evaluation the following methods can be applied: • • • •

classified costs and values: division in cost and value classes estimated qualitative costs and values: estimation by calculation or experience normative costs and values: limit values presented in norms and standards ranking of the importance of costs and values: ranking list based on the weighting of different costs and values in numerical calculations • intuitive valuation: valuation based on intuitive valuation of one or more people involved in the design. The financial life cycle cost components of structural assemblies should be presented in future, for example in the suppliers’ product descriptions. They can also be collected into a contractor’s statistics database or into general design manuals, such as Life Cycle Costing for Design Professionals (Kirk and Dell’Isola 1995). Environmental costs are calculated in the detailed design phase with the same equations (3.1)–(3.3) as in the conceptual design phase, but with more precision, using suppliers’ product information, contractors’ environmental statistics or general environmental statistics, such as manuals and computer tools (Lippiatt 1998a, Lippiatt 1998b). 3.2.3 Design life Design life is a specified time period, which is used in calculations. Ordinary design life is 50 years (CEN 1991) for buildings and 100 years for civil engineering structures. In special cases even longer design life cycles can be used. However, after 50 years the effect of increased design life cycle is quite small and it can be estimated as the residual value at the end of the calculation life cycle. Temporary structures are designed for a shorter design life, which will be specified in each individual case. In ENV 1991–1 the following classification of design life is presented: Class 1:1–5 years Class 2:25 years Class 3:50 years Class 4:100 years

Special case temporary buildings Temporary buildings, e.g. stores buildings, accommodation barracks Ordinary buildings Special buildings, bridges and other infrastructure buildings or where more accurate calculations are needed, e.g. for safety reasons Class 5: over 100 years Special buildings e.g. monuments, very important infrastructure buildings 3.2.4 Estimation of recycling efficiency The components of the environmental profile of basic materials already include recycling efficiency-the environmental costs of materials recycling. It is important to realise that in design, the recycling potential of building components, assemblies and even technical systems must be considered. The higher the recycling is in the building’s heirarchy, the higher the ecological and economic efficiency of the recycling will be. At the conceptual phase, the estimation of recycling efficiency is typically using the recycling efficiency indices of the structural assemblies or components. The estimation of the recycling efficiency indices of

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different alternative solutions of structural systems or assemblies can be carried out by applying the scheme presented in Table 3.4. Rough estimates of the recycling efficiency are: 1 Recycling of materials: • consumption of raw materials 0.5–0.9 • consumption of energy 0.0–0.5 • production of pollutants 0.1–0.7 2 Recycling of structural or installation assemblies or components: • consumption of raw materials 0.7–0.9 • consumption of energy 0.7–0.9 • production of pollutants 0.8–0.9 3.2.5 Estimation of residual value The residual value of different modules of the building at the end of design life time (e.g. 50 years) can be estimated with the same statistics and methods that are used in taxation and insurance contexts. The producers’ service life can also be used in calculating the residual value with the equation (3.1)

3.2.6 Energy costs of the building Basically the calculation of life cycle energy costs is part of the calculation of environmental life cycle costs. However, because of the great importance (typically about 80 per cent of all environmental burdens) of energy in life cycle environmental costs, and because of its considerable impact also in financial life cycle costs of the building, the methods in calculations of life cycle energy are outlined briefly below. Energy costs are determined at the draft design phase depending on the functional and technical specifications of the building. The following classification of buildings can be roughly used for definition of, and decisions about, the energy costs of the building at sketch and draft design phase: Class 1. Standard level. Heating/cooling energy costs appropriate to current standards of the country or region. Heating/cooling energy consumption is typically 120–180 kWh/m2y and total energy consumption is 150–200 kWh/m2y. The area being calculated as a living floor area. Table 3.4Estimation of the recycling efficiency coefficient kr Recycling factor Basic value Separability

Basic value and residual changes of the recycling factor at the level of Building

Asssembly

Component

Material

0.6

0.5

0.4

0.2

LIFE CYCLE DESIGN METHODS

Recycling factor

35

Basic value and residual changes of the recycling factor at the level of

−High −Moderate −Low Moveability −High −Moderate −Low Reintegrability −High −Moderate −Low Final value

Building

Asssembly

Component

Material

+0.2 0.0 −0.2

+0.2 0.0 −0.2

+0.2 0.0 −0.2

+0.2 0.0 −0.1

+0.05 0.00 −0.05

+0.05 0.00 −0.05

+0.05 0.00 −0.05

+0.05 0.00 −0.050

+0.1 0.0 −0.1 0.25…0.90

+0.1 0.0 −0.1 0.15…0.85

+0.1 0.0 −0.1 0.10…0.75

+0.1 0.0 −0.1 0.00…0.55

Class 2. Reduced energy level. Heating/cooling energy consumption of 60–80 kWh/m2y and total energy consumption (including lighting and other building services systems use) less than 100 kWh/m2y. Class 3. Low energy level. Heating/cooling energy consumption of 30–40 kWh/ m2y, and the consumption of total energy (including lighting and building services systems use) less that 60 kWh/m2y. Class 4. Zero energy level. Heating/cooling energy consumption is zero. This needs active solar energy gain or some other natural energy source such as from the earth. Class 5. Energy gain building The gain from solar or other natural energy is more than that needed for heating/cooling and building services systems. 3.3 Generic systematics from requirements into technical specifications 3.3.1 Classification of users' requirements The following is a systematised classification of the functional requirements (Leinonen and Huovila 2000), applying the systematics of CIB Master List. This list can be used as a check-list in requirements analysis. This functional requirements list is as follows: A Performance A1 Conformity A1. Core processes 1 A1. Supporting processes 2

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A1. Corporate image 3 A1. Accessibility 4 A2 Location A2. 1 A2. 2 A2. 3 A2. 4

Site characteristics Transportation Services Loadings to immediate surroundings

A3 Indoor conditions A3. Indoor climate 1 A3. Acoustics 2 A3. Illumination 3 A4 Service life and deterioration risks A4. Service life 1 A4. Deterioration risks 2 A5 Adaptability A5. Adaptability in design and use 1 A5. Space systems and pathways 2 A6 Safety A6. Structural safety 1 A6. Fire safety 2

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A6. Safety in use 3 A6. Intrusion safety 4 A6. Natural catastrophes 5 A7 Comfort B Cost and environmental properties B1 Life cycle costs B1. 1 B1. 2 B1. 3 B1. 4

Investment costs Service costs Maintenance costs Disposal and value

B2 Land use B3 Environmental burdens during operation B3. Consumption and loads, building 1 B3. Consumption and loads, users 2 B4 Embodied environmental impacts B4. 1 B4. 2 B4. 3 B4. 4 B4. 5 B4. 6

Non-renewable natural materials Total energy Greenhouse gases Photochemical oxidants Other production related environmental loads Recycling

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C Requirements of the process C1 Design and construction process C1. Design process 1 C1. Site operations 2 C2 Operations C2. Usability 1 C2. Maintainability 2 3.3.2 Phases of performance-based design procedure Integrated lifetime engineering methodology aims to regulate optimisation and ensure life cycle human conditions, economy, cultural compatibility and ecology through technical performance parameters, as presented in Figure 0.1. With the aid of lifetime engineering we can thus control and optimise the human conditions (safety, health and comfort), the financial costs and environmental costs. Beside these, social aspects also have to be taken into consideration. The phases of performance-based planning and design are: 1 analysis of the functional and performance requirements of the user 2 analysis and optimisation of the performance properties of the structure based on the functional requirements of the user 3 specification of the technical properties of the structure, based on the performance properties. The procedural schema is as presented in Figure 3.4. 3.3.3 Quality function deployment method The quality function deployment (QFD) method is related to linear programming methods which were widely used in the 1960s in industrial product development. As currently formulated QFD was developed in Japan and was first used in 1972 by the Kobe Shipyard of Mitsubishi Heavy Industries (Zairi and Youssef, 1995). After that QFD has been increasingly used in Japan and since the 1980s also in the USA, Europe and worldwide. Until now its main use has been in the mechanical and electronics industries, but applications also exist in construction.

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Figure 3.4 Procedural schema from functional requirements to technical specifications

QFD is used to translate requirements into either functional or technical specifications. Thus QFD can serve as an optimising or selective linking tool between requirements and specifications. It can be used both for product development or for the design of individual buildings. Fundamental objectives of QFD are: • identification of customers’ needs • interpreting customer needs first into the functional and then into the technical specifications of the building • optimising the technical solutions with regard to requirements • selection between different design alternative Put simply, the QFD method requires the building of a matrix between requirements (the ‘whats’) and design specifications (the ‘hows’). The priorities of requirements, priorities of specifications, and the correlation between requirements and correlation between specification can also be undertaken. In practical design applications it is limited to a few key requirements and specifications in order to maintain good control of variables and to avoid wasting efforts on secondary factors. At product development a more detailed application can be used. The principle of key attributes and parameters can be applied differently to each type of design case in order to get an optimal use of QFD method. A model table—a ‘house of quality’—is presented in Figure 3.5. In industrial engineering, manufacturing companies have successfully applied concurrent engineering tools, such as quality function deployment (Akao 1990) to include customers’ needs for product features into design at early stages of development, to integrate concurrent design of products and related processes, and to consider all elements of the product life cycle. Customer-oriented ‘champion products’ may also be priced higher than their competitors, and still become market leaders. In spite of its success stories in other industries during the past decade, QFD has rarely been applied in construction. However, examples from Japan, the United States, Finland, Sweden and Chile show it also has potential in building design. (Nieminen and Huovila 2000). QFD provides an empty matrix (‘house of quality’, Figure 3.5) to be filled with customer requirements and their importance in the rows along the left-hand side, and properties of the solutions in the columns along the top portion. The centre describes the matrix-relationship of requirements and corresponding

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Figure 3.5 A ‘house of quality’ (Nieminen and Huovila 2000)

solutions. The importance measures (weighting factors) are at the bottom, and the right- hand side of the box shows the evaluation of competing alternatives. The following phases of a construction process are identified as potential for QFD implementation in construction, Figures 3.5 and 3.6 a and b: 1 2 3 4

programming: customers’ requirements for building and design objectives design: design objectives and construction drawings production: construction drawings and production plans construction: production plans and construction phases. Priorities of design specifications

The following procedure can be applied when using QFD to analyse functional requirements against owners’ and users’ needs, technical specifications against functional requirements, and design alternatives or products against technical specifications: 1 2 3 4 5

identify and list factors for ‘what’ and ‘how’ evaluate and list priorities or weighting factors of ‘whats’ evaluate correlation between ‘whats’ and ‘hows’ calculate the factor: correlation times weight for each ‘how’ normalise the factor: ‘correlation times weight’ of each ‘how for use as a priority factor or weighting factor of each ‘how’ at the next stage.

A schedule for analysis between primary functional attributes and technical specifications can be presented as shown in Figure 3.6b. Technical specifications priorities can again be used as weighting factors for comparisons between different design alternatives and products regarding owners’ and users’ demands and requirements. The following two case studies illustrate similar schemes (Nieminen and Huovila 2000).

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3.3.4 Examples CASE STUDY 1: VILLA 2000 The design of Villa 2000 was based on teamwork, where each designer could influence decision-making in other design fields outside his own design Figure 3.6a Demands and their priorities Correlation between ‘hows’ Primary functional attributes 1 Primary demands

2

3

4

5

Correlation between ‘hows’ and ‘whats’ c

Priorities of demands, p

1. Financial costs 2. Functionality 3. Environmental costs 4. Health 5. Aesthetics (c×p)

1.0 0.5 0.2 0.5 0.3 0.0 1.0 0.0 0.1 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.1 0.0 1.0 0.2 0.0 0.0 0.0 0.2 1 9.0 15.6 9.6 15.7 12.7 Priorities of functional attributes =c×p/ (c×p) 0.14 0.25 0.15 0.25 0.20 Primary functional attributtes1 Life cycle financial costs 2 Life cycle functionality 3 Life cycle maintenance 4 Life cycle environmental costs 5 Health, aesthetics and comfort

9 10 8 10 8 =62.6

Figure 3.6b Functional attributes and their priorities Correlation between ‘hows’ Primary technical specifications 1 Primary functional attributes 1 2 3 4 5 (c×p)

2

3

4

5

6

7

8

9

10

Correlation between ‘hows’ and ‘whats’, c 0.3 0.2 0.2 0.2 0.0 0.0 0.0 0.5 0.3 0.3 0.3 0.0 0.2 0.2 0.5 0.5 0.4 0.1 0.0 0.1 0.1 0.2 0.1 0.1 1.8 1.0 0.0 0.0 0.0 0.0 0.0 0.4 0.2 0.3 0.3 13.8 10.1 9.2 16.1 10.0 18.0 5.9 Priorities of functional attributes=c×p/ (c×p) 0.11 0.08 0.08 0.08 0.13 0.15 0.005

0.0 0.1 0.1 0.0 0.1 2.9

0.0 0.3 0.2 0.1 1.0 15.6

0.3 0.3 0.8 0.3 0.5 20.3

0.02

0.13 0.17

Priorities of functional attributes 9 10 9 8 10 =121.9

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Correlation between ‘hows’ Primary technical specifications 1

2

3

Primary funcctional attributees 1 Product structuring for changes and reuse 2 Service life specifications 3 Static and dynamic specifications 4 Energy specifications 5 Environmental specifications

4

5

6

7

8

9

10

6 Hygrothermal specifications 7 Acoustic specifications 8 Fire safety specifications 9 Health specifications 10 Maintainability and repairability

responsibilities. A design briefing process was organised to acertain the owners’ requirements for the building. The QFD method was used experimentally to set design guidelines for Villa 2000. The IEA Task 23 criteria were expressed in a form of performance requirements and they are given weights (on a scale of 1 to 5) depending on their importance (IEA 1998). The potential design solutions are then created in the form of properties and their correlation with the requirement is given (on a scale of 0, 1, 3 or 9). The QFD spreadsheet summarises numeric values of the properties at the bottom of the matrix by multiplying the correlation with their weights, so that high values indicate high priorities. The user may then select the most important properties as a basis for the next phase of development. The exercise was conducted with a group of ten experts from different backgrounds. The following objectives were set for the working session: • to share common understanding of the performance-based objectives of the end product (a building to be designed and constructed) • to prioritise the project objectives • to strive for innovative design solutions that meet these objectives. The first matrix (Figure 3.7a) shows the main selected objectives of a housing project (adaptability, indoor conditions, economy, environment friendliness, constructability and architecture) used as a basis for building design. The second matrix (Figure 3.7b) shows the structured approach in the design process based on the selection made in phase 1. The importance of the whole design and construction process was recognised as the key to fulfil the requirements, and the functionality and adaptability of the house as the key to future housing. CASE STUDY 2: NURSERY SCHOOL The second QFD example was to set the project objectives with a view to the building users’ needs and requirements and to show how the chosen criteria and the users’ view affect the results. The QFD matrix was used to acertain, record and verify the clients’ requirements and to test the dependency between the requirements and the properties of the proposed building concept. The project used in the test was a nursery school for about 100 children built in the year 2000. The design process of the building was finished towards the end of 1999, based on an architectural competition. The Merituuli nursery school was built in a new suburban housing area, formerly an industrial area, where the basic infrastructure was already developed (streets, access to main roads, district heating network, etc.). The

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Figure 3.7a Design objectives for a housing project, phase 1 (Nieminen and Huovila 2000)

Figure 3.7b Design objectives for a housing project, phase 2

location of the area is very close to the city of Helsinki with good public access to the city, which has made the area very popular, especially among young families. This has also grown to be a design feature for the nursery school building and its connection to the surrounding housing area. The building serves as a nursery school during the daytime, and in the evening as a meeting point for community activities. The total building area is 1260 m2 in a single storey. The owner of the building is the City of Helsinki, and the Construction Management Division (HKR) of the City of Helsinki constructed the building. In a number of development sessions arranged between the client and VTT (Technical Research Centre of Finland) at the beginning of the project and, later between the designers, project management and VTT, the project goals and limits were discussed and the requirements were set. The decision-making in the project was tested against the main criteria adopted from the IEA Task 23 framework.

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The results of the design briefing sessions were used as building owner-defined sub-requirements in compiling the QFD matrix (Figure 3.8). According to the QFD results, the main properties of the nursery school building corresponding to the given requirements are district heating, bicycle access to the site, cleanable ventilation ductwork, multi-use playrooms for children and low-energy building envelope. Environmental goals of the project were prioritised as the most important properties. Even though the builder has an environmental programme to support sustainable construction, it is not surprising that the requirements dealing with functionality or air quality in a nursery school dominated the pre-design process. QFD method was used to evaluate the proposed technical design solution and to compare the design with typical existing nursery schools. A low-energy concept for the nursery school was also developed and analysed accordingly. The proposed solution (basic design, Figure 3.9) shows improvements compared to typical nursery schools. By improving the energy efficiency of the building, both user-friendliness (functionality, indoor climate) and environmental properties and life cycle costs were improved. 3.4 Multiple-attribute analysis, optimisation and decision-making (MADA) 3.4.1 Background to the method The main phases of the life cycle design procedure are: analysis of the actual requirements, interpretation of the requirements into technical performance specifications of structures, creation of alternative structural solutions, life cycle analysis and preliminary optimisation of the alternatives, selection of the optimal solution between the alternatives and finally the detailed design of the selected structural system. Multiple criteria optimisation is a central tool of structural designers in supporting decisions at the conceptual phase of design. The decisions, even in integrated design procedure, will be mainly based on empirical knowledge of the decision-makers, but supported by mathematical multiple-criteria analysis and multiple-variable optimisations (Baumann 1998). In this section the multi-attribute decision analysis method (MADA), which includes several variables is examined. (See also descriptions in Roozenburg and Eekels 1990, Lippiatt 1998a and 1998b, ASTM 1995, Norris and Marshall 1995.) The analysis made by Norris and Marshall (1995) shows, that in some cases where qualitative and quantitative financial and non-financial attributes are included in multi-attribute decision-making, a modified MADA method, non-traditional capital investment criteria (NCIC) is more suitable. NCIC developed by Boucher and Mac Stravic as a multi-attribute evaluation within a present worth framework and its relation to the analytic hierarchy process. This is also the case in structural design when dealing with comparison, selection and optimisation between several alternatives of structural systems, modules, components or materials. For this reason, only the NCIC method is presented here where it is applied to structural design. 3.4.2 Multi-attribute decision analysis (MADA) method and its modification NCIC In the integrated life cycle design of structures the structural systems, modules, components and materials have to be analysed for selection between alternatives. The NCIC method incorporates a paired comparison procedure together with a pre-specified approach for converting the comparisons into attribute weights. The method allows hierarchical description of problems in order to keep the number of pairwise comparisons

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Figure 3.8 Design priorities for a nursery school (Nieminen and Huovila 2000)

Figure 3.9 Analysis of two design solutions and comparison to properties of a typical nursery school building

manageable. In structural design the hierarchical levels are: structural system, modules, components and materials. The method can deal with numerical quantitative values of attributes and with descriptive qualitative values of attributes. One of the attributes is always measured in monetary units attributed to each performance gain, and these values are summed to yield the overall implied value of each alternative. These implied values can be used to select an alternative, to rank alternatives, or to screen alternatives. The NCIC method is compensatory, which means that a high performance relative to one attribute can at least partially compensate for low performance relative to another attribute. However, minimum performance requirements have to be met.

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3.4.3 MADA procedure in structural design The MADA analysis can be used as a tool for multi attribute or multi-criteria optimisation and decisionmaking MCDM. MCDM includes analysis, comparison and selection procedures during the following phases: 1 2 3 4 5 6 7 8

definition of hierarchical levels to be dealt with definition of attributes and their weights definition of structural alternatives to be compared on each level of hierarchy calculation of numerical score and a total value of each alternative calculation of the incremental value of each alternative from each attribute calculation of total value of each alternative coupled comparisons of alternatives with the aid of their numerical core attributes ranking of the alternatives primarily in regard to numerical core attributes but also rin regard to incremental value attributes or total value 9 selection of the best alternative for further design. It is obvious that all minimum requirements of general laws, norms and standards must be fulfilled. 3.4.3.1 Attributes and their weights Typical attributes and sub-attributes of structures are presented in Table 3.5. In special cases the attributes can be modified and changed if these general attributes do not reflect the actual needs. Life cycle monetary costs and functionality as primary attributes are always numerical. Therefore functionality must be evaluated numerically using the QFD method. Because of two existing primary attributes (monetary life cycle cost and functionality) we can apply their ratio: functional efficiency (functionality/cost) as a primary attribute in comparisons. In that case pure values of life cycle cost and life cycle functionality can be treated as incremental values. Table 3.5 General attributes and sub-attributes of structures Attribute

Subattribute

1 Life cycle monetary costs

Construction cost Energy cost during design service life Maintenance cost during design service life Repair costs during design service life Changing costs during design service life Renewal costs during design service life Recycling cost Disposal cost Functionality for the first user Flexibility for changes of building services Flexibility for spaces Flexibility for changes in performance of structures Reliability in operation in normal and abnormal conditions

2 Life cycle functionality

3 Life cycle maintenance

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Attribute 4 Life cycle environmental costs

5 Health and comfort

47

Subattribute Ease, frequency and staff requirements of maintenance Consumption of energy: renewable/ non-renewable/fossil Consumption of raw materials: renewable/ non-renewable Production of pollutants and disposals into air, soil and water Internal air quality (emissions) Working conditions during construction Hygrothermal quality of internal conditions Acoustic and visual privacy and convenience Visual quality and aesthetics

Note: Commonly dominant attributes or subattributes that dictate about 70–80 per cent of actual life cycle costs or value of buildings are shown in bold.

The life cycle monetary and environmental costs are mainly calculated numerically with relevant calculation methods. Functionality as a primary attribute must be evaluated numerically using the QFD method. The other attribute values are mainly presented descriptively, but also partly numerically, and the values are divided for example intofour classes: very high, high, moderate and low. Some of the values, like environmental costs, are negative. Each primary attribute is evaluated as a weighted sum of its subattributes for calculating the increment values of each attribute in the case of each alternative.

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Figure 3. 10 Hierarchy of the structural system of buildings (Sarja 1989)

3.4.3.2 Hierarchical levels Life cycle optimisation increases the need for a hierarchical system approach, where buildings or other structural systems are considered as different entities, starting from sub-buildings, technical systems or modules and ending at components and their details (Sarja 1989, Sarja and Hannus 1995). The comparisons and selections are generally made first on a complete building level, modularising the building into technical systems, In structural design the following hierarchical levels are used: 1 structural system 2 structural module: such as the loadbearing frame (or superstructure), foundations, envelope, partition walls, connection modules (staircases), roofing 3 structural components: such as a beam, a column, a slab etc. 4 materials and details finishing, plastering, water proofing membranes of floors and roofs, joints, floorings, paintings, furniture etc. The hierarchy of the structural system is presented as an example in Figure 3.10. 3.4.3.3 Alternatives at each level of the hierarchy The first phase for the definition of structural alternatives is the creative design work phase and will produce ideas for the structural system and its key modules. In building design the key modules can often be used as a start for the entire structural system. The key modules are usually the loadbearing frame, including the floors, and the envelope. At the creative phase the attributes and their weights already serve as an intuitive

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background. Systematic methods of creative product development can also be applied. The result of this definition are a set of probably between two and four alternative structural systems and their key modules. 3.4.3.4 Numerical score and total implied value of each alternative The first step in the selection procedure is the calculation of numerical score vi1, where i is the number of the alternative. The numerical score vi1 is always calculated in present value monetary units over the entire design service life. Thus it represents the first attribute: ‘financial cost’. This means that financial cost is isolated as a dictating factor, and the other factors are treated as incremental values. The cardinal numerical score vi1 is calculated as a present value of life cycle monetary costs using separately the methods described here. The present value can be calculated either directly by the current value method, or through annual values converting them later into present value over the design service life period. Because there are two existing primary attributes (financial life cycle cost and functionality) we can apply their ratio: functional efficiency (functionality/cost) as a primary attribute in comparisons. In this case pure values of life cycle cost and life cycle functionality can be treated as incremental values. The life cycle monetary and environmental costs are mainly calculated numerically with relevant calculation methods. Functionality as a primary attribute can be evaluated numerically using the QFD method, or it can be evaluated. Each attribute j other than the financial cost attribute, contributes an independent increment of value vij, to the total value of the alternative i. The increment of value vij can be either positive or negative. The costs related to each attribute are calculated as negative values and the benefits as positive values. Usually only the monetary value vi1 and some other attributes (often only some sub-attributes), like environmental costs, are calculated numerically. The other attributes are expressed as descriptive qualitative values: ‘very high’, ‘high’, ‘moderate’ and ‘low’. The total implied value Vi of each alternative i is calculated as the sum of the value increments associated with its performance relative to each of the n leaf attributes, applying the linear equation (3.4) Vi is used to identify a subset of most preferred alternatives, to rank the alternatives, and to select the single most preferred alternative. The weight coefficients of the alternatives are defined separately for each alternative. Thus, the weight coefficients are not necessarily exactly constant across alternatives, because the importance of each attribute may be different between alternatives. Therefore the weight coefficients of this method do not characterise exactly the general relative importance of the attributes. 3.4.3.5 Incremental values of attributes At the second step, the incremental values of each attribute j of each alternative i have to be normalised, because they have different qualitative or quantitative measures. This is done comparing the value of each attribute to the value of a chosen baseline alternative 1, which usually represents the most ordinary alter native. Thus, the modified (normalised and weighted) incremental value vijm is calculated with the equation (3.5)

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3.4.3.6 Total implied value of alternatives The modified total implied value Vim of alternative i is calculated with the equation (3.6) Each normalised and weighted incremental value vijm thus varies between vijm=± (0,Kij), where kij is the weight coefficient of the attribute j of alternative i. 3.4.3.7 Pairwise comparisons of alternatives At the first step, at each alternative the pairwise comparison of attributes is made ranking the importance of each attribute in that alternative. This procedure produces the weight coefficients between the attribute of each alternative. 3.4.3.8 Retrofitting alternatives During the selection procedure some alternatives may show a need for changes in order to improve performance and thus the value. This retrofitting is defined as modifying the alternative in order to improve its performance. After retrofitting the primary numerical score value and the total implied value is calculated again. 3.4.3.9 Selection of the alternatives for further design The selection can be made by including the comparison of monetary life cycle costs together with multiple, conflicting non-monetary attributes of alternatives. The NCIC method is designed to make explicit the implied monetary value of the non-financial benefits. The results of an NCIC analysis can also be integrated into traditional economic analysis. Often the factors of the environmental profile are quite well interrelated, which makes comparisons and optimisations easy (United States Environmental Protection Agency (USEPA) 1990, Norberg-Bohm, Clark, Bakshi, Berkenkamp, Bishko, Koehler, Marrs, Nielsen and Sagar, 1992). Sometimes different components have different optimum points. In such cases, a valuation between the components with different measurement systems (for example, costs are measured in currency, whereas air pollution is measured in tons of CO2 and NOx) must be done by using suitable weighted coefficients and normalised values for the components (Udo de Haes, Jolliet, Finnveden, Hauschild, Krewitt, and MüllerWenk 1999, Sarja 2001). Normalisation can be done by comparing all alternatives with a commonly-known reference alternative and dividing the corresponding values of each valuation component. Complicated analysis can, in design, be done for very large and important building projects and in the development process of entire building concepts or building products. In the design of ordinary buildings the method can be used in simplified ways. The numerical value of the cardinal numerical score (the present value of costs over design life time period) has always to be calculated using general characteristic values at a level of functional units like spaces and structural modules. A simple calculation of total implied value of each alternative on a hierarchical level corresponding to the monetary cost calculations can also be made.

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The selection can be based on partly intuitive and subjective decisions by the client or owner, although this should be supported by the analysis made by the structural designer. The alternatives selected subjectively may be: • the alternative with lowest life cycle monetary cost, together with at least moderate total implied value and at least moderate values of important individual attributes • the alternative with reasonable life cycle monetary cost together with highest total implied value • the alternative with reasonable life cycle monetary cost together with high incremental values of most important attribute(s) and at least moderate incremental value of other attributes. An example scheme of a decision table is presented in Table 3.6. 3.4.3.10 Values of variables In analysis, optimisation and decision-making, the following types of values of variables are used: 1 2 3 4 5 6

calculated numerical financial and environmental costs and values classified costs and values estimated qualitative costs and values normative costs and values ranking of the importance of costs and values intuitive valuation. 3.4.4 Integration of the design solutions

To integrate partial design solutions, which are produced by selecting between alternatives, applying the design tasks and methods described above, an additonal aggregation of performance parameters will be made followed by multi-attribute analysis and decision-making. The result will be a final definition of the technical performance parameters of structures and materials. The results will then be used as design criteria specifications in the subsequent finalising of the detailed design of the structure. Table 3.6 An example decision-making table Primary attributes

Limit or weighting factors specified by client

Construction cost E(0) life cycle cost (design life cost) Etot(td) Euro max E(0)=55 000 max Etot(td)=105 000

Incremental values Lifetime usability and changeability score/ranking (scale: 4–10)

Health, safety, convenience score/ranking (scale: 4–10)

Environmental cost relative ecoefficiency/ ranking

Cultural value score/ ranking (scale: 4–10)

Weighting factor=10

Weighting factor =10

Weighting factor=8

Weighting factor=8

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Primary attributes Alternatives Reference alternative 1 Alternative 2 Alternative 3 Ranking2

R=52 000 E=105 000 R=55 000 E=103 000 R=53 000 E=104 000 All alternatives fulfil the requirements –

Incremental values 8.0 (3rd)

8.5 (3rd)

1.0 (3rd)

7.0 (3rd)

9.0 (1st)

9.5 (1st)

1.3 (1st)

8.5 (2nd)

8.5 (2nd)

9 (2nd)

1.1 (2nd)

9 (1st)

1st Alternative 2 2nd Alternative 3 3rd Alternative 1 85.0 95.0 90.0

1st Alternative 3 2nd Alternative 3 3rd Alternative 1 56.0 62.0 52.5

1st Alternative 2 2nd Alternative 2 3rd Alternative 1 56.0 68.0 72.0

1st Alternative 2 2nd Alternative 3 3rd Alternative 1 Numerical score 80.0 90.0 85.0 Residual value Alternative 1: 25 000 euro after design life Alternative 2: 29 000 euro time (50 years) at Alternative 3: 28 000 euro present value Final ranking Ranking 1: Alternative 2=315.0 and numerical Ranking 2: Alternative 3=299.5 score Ranking 3: Alternative 1=276.5

3.4.4.1 Aggregation of life cycle performance parameters Because of the complexity of building systems, decisions between design alternatives for the building, as well as between its technical system, module and product alternatives, must be simplified so as to limit the number of parameters used in the final decisions. To achieve this a number of design parameters will be aggregated. As described earlier, the final objective of the integrated life cycle design is optimised life cycle quality which consists of four dominant parameters (see Figure 1.2): 1 2 3 4

life cycle functionality life cycle costs life cycle ecology life cycle human conditions

A practical procedure in design is to use these four quality parameters as primary criteria parameters when selecting between design alternatives and products. They are referrred to here as ‘life cycle quality parameters’, LCQ. Each life cycle quality parameter consists of a set of technical performance parameters. The process of building the relation between a life cycle quality parameter and its technical performance parameters is called aggregating. The methods used in aggregating are presented in Table 3.7.

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3.4.4.2 Aggregation procedure An important phase of the optimisation or decision-making procedure is the aggregation of a large number of specific performance factors into the LCQ parameters presented in Table 3.7. The aggregation scheme of LCQ parameters is presented in Figure 3.11. The weighting in aggregation of environemental parameters is made on the following levels: 1 global level 2 regional level 3 local level Typical global factors, which always have a high weight are the consumption of energy and air pollution which include factors of global climatic change. Typical regional factors are, for example, consumption of raw materials and water. In locations these factors are extremely important, but in others they, or some of them, have little relevance. The weighting between safety, health and comfort can be made individually. Usually the weightings of health and safety are very high, while the weighting of comfort can vary more widely. In any case, health and safety must fulfil the minimum regulatory requirements, which usually are quite strong. As an example we can take the weightings in northern Europe (Scandinavian countries). A weighting, where the factors of climatic change and air pollution (CO2 ekv, SO2 ekv and ethane ekvivalent) are taken into account is widely used (Lindfors et al. 1995). Table 3.7 Methods used in agregating life cycle quality (LCQ) parameters from technical life cycle parameters Life cycle quality parameter

Aggregation method

Criteria

1 Life cycle functionality (QFD)

Quality function deployment Normative minimum requirements and classifications Life cycle costing

Functional efficiency

2 Life cycle financial costs (LCFC)

3 Life cycle environmental costs (LCEC) 4 Life cycle human conditions (LCHC)

5 Overall Life Cycle Quality

Economic efficiency (Normative minimum requirements and classifications) EPA Science Advisory Board (1990), Ecoefficiency Normative minimum Lippiatt (1998b) Harvard University requirements and classifications Study (Norberg-Bohm et al. 1992) Analysis of total volatile organic Quality classifications of indoor air compounds (VOC) emissions quality and other indoor air (Radnünz 1998). conditions. Evaluation of fungal risk. Evaluation Quality classifications of acoustic of risk of radioactive radiation from performance. materials and from the earth. Normative minimum criteria and Evaluation of ventilating air quality. classifications of safety, health and Evaluation of health risks to water comfort. quality. Multi-attribute decision-making Life cycle quality (LCQ)

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Figure 3.11 Aggregation scheme for LCQ parameters

3.4.4.3 Normalised ecoefficiency parameter The general aggregated environmental life cycle environmental cost (LCEC) value, which is described above, can be used in calculating the normalised ecoefficiency parameter (ECOEFF). ECOEFF can be calculated as a ratio between LCEC of a reference object (product, design solution, building concept, production method etc.) and the LCEC of the actual object, using the equation (Sarja 2001). (3.7) where ECOEFF is the normalised ecological efficiency parameter LCECref life cycle environmental cost parameter LCEC of the reference object LCECactual life cycle environmental cost parameter LCEC of the actual object

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3.5 Service life planning 3.5.1 Objective and principles The objective of service life planning is to ensure that the service life of a building, its modules and components are functionally, technically, ecologically and economically optimised over the design life. However, the service life of different parts (modules or components) of a building are different. Also the decisive factor dictating service life varies, it may be defective performance, or functional, technical, ecological or economic obsolescence. From experience, we know that roughly 50 per cent of buildings are demolished because of defective performance and 50 per cent are demolished because of obsolescence. This dictating factor has to be identified separately at life cycle planning process for each part of the building, and for each alternative design or product. Once identified, the optimisation of the system through sequential comparisons between alternatives can take place. Because of the multiple categories of requirements, some feedback during the planning process is needed, which is why the process is partly iterative. The service life of buildings and their subsystems, modules and components can be classified, for example by using the classification presented in Chapter 2. Another classification is presented in draft Standard ISO/DIS15686–1. The rough classification serves as a framework for service life planning and optimisation at briefing, conceptual and initial design phases, but more exact service life estimation is carried out at detailed design phase during selection between different products. A model of modularised service life planning scheme is presented in Table 3.7. As can be seen, the target service life of some key modules like foundations and loadbearing frame can be defined as being longer than the design life of the building. This means that those modules retain a certain residual value after the design life, which can be taken into account in economic life cycle calculations both of financial and environmental costs. Following the scheduled target service life, a multiple requirements life cycle optimisation can be made spearately for each building. The optimisation is carried out in order to determine optimal target service life values above the design service life of building, and optimal target service life inside the specified range of possible suitable values as presented in Table 3.8. A model applying the residual value method for modules having a characteristic service life above the calculated value for the building, and applying a method of multiplication coefficients for modules having several changes or renewals during the design service life of the building are presented in Table 3.9. 3.5.2 Service life dictated by defective performance Defective performance is controlled in design with proper service life planning which results in realistic target service life for key modules of the building, and in detailed durability service life design which results in key structures which are owing an adequate performance over design service life.

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3.5.3 Service life dictated by obsolescence Obsolescence means the inability to satisfy changing functional, technical or economic requirements. Obsolescence can affect the entire building or just some of its modules or components. Functional obsolescence is due to changes in functions and use of the building or its modules. This can even be when the building’s location becomes unsuitable. This has commonly happened in country areas when people have moved into cities. In such cases the only possibility would be to dismantle and reassemble the building, which would require a demountable structural system. More common are changes in use which require changes in functional spaces or building services systems. This gives rise to a need for flexible structural systems, usually requiring Table 3.8 A model of modularised service life planning schame of a building with a design life of 50 years Ordinary target/design life due to Functional module Functional obsolescence (years)

Technical obsolescence (years)

Economic obsolescence (years)

Defective performance (years)

Target service life (CSL) (years)1

Foundations >100 >100 >100 50–>100 >=50 Loadbearing >1002 >100 >100 50–>100 >=50 frame Envelope/walls >50 >50 50 30–200 30−>50 Envelope/roof 50 50 50 15–>100 20–>50 Envelope/ ground >50 >50 >50 30−>100 >=50 floor Envelope/ 30–50 20–50 20–50 20–50 >=303 windows Envelope/doors >=20 20–30 >50 30–>100 20–>503 Partition floors3 1–50 20–50 >100 >100 >=505 Partition walls 5–50 >50 >50 40–>100 5–503 4 (including doors)3 Bathrooms and 20–30 15–30 25–40 20–>50 20–505 2 kitchens3 Building services 2–40 3–50 3–50 5–40 5–405 3 systems Notes 1 Target or design life will be defined inside the defined range through multiple requirements optimisation process. 2 Flexibility for changes of internal spaces is needed in periods of changes of other modules. 3 Recycleability of components is important. 4 Modules include compatibility between structures and installations. 5 Changeability of parts of module is highly needed.

long spans and minimum numbers of vertical loadbearing structures. Partition walls and building services systems which are easy to change are also required. Changes in building services systems equipment are often the cause of technological obsolescence, but the structure can also be a cause when new products providing better performance become available. Typical examples are more efficient heating and ventilation systems and their control systems, new

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information and communication systems such as computer networks, better sound and impact insulation for floorings, and more accurate and efficient thermal insulation of windows or walls. Technological obsolescence can sometimes be avoided or reduced by estimating future technical development when selecting products. The effects of technical obsolescence can also be reduced through the proper design of structural and building service systems to allow easy change, renewal and recycling. Economic obsolescence means that operation and maintenance costs are too high in comparison to new systems and products. This can partly be avoided in design by carefully minimising the operation and costs by selecting materials, structures and equipment which need minimum amounts of work and materials for maintenance and operation. Often this means simple and safe working products Table 3.9 Residual value method and multiplication coefficient method in the optimisation of target service life of building modules (the building has design life of 50 years) Functional module

Target service Residual R 50 after life (design design service life service life, DSL) of 50 years 1 (years)

Multiplication coefficient C during design service life of 50 years

Estimated time period for functional changes in actual building years

Multiplication coefficient C for further calculations

Foundations Loadbearing frame Envelope/walls

>=50 >=502

(DSL–50)/DSL (DSL–50)/DSL

1 1

– –

1 12

30–>50

1–2

–

1–2

Envelope/roof

20–>50

1–3

–

1–3

Envelope/ground floor Envelope/ windows Envelope/doors

>=50

0–(DSL–50)/ DSL 0–(DSL–50)/ DSL (DSL–50)/DSL

1

–

1

2

–

2

1–2

–

1–2

Partition floors3 Partition walls (including doors)

>=505 5–>03 5

0 to second residual value 0–(DSL–50)/ DSL (DSL–50)/DSL 0–(DSL–50)/ DSL

1 1–10

– CW=5–50

1–2 1